GB2507152B

GB2507152B - Process and apparatus for modelling an ambient field

Info

Publication number: GB2507152B
Application number: GB1314268.2A
Authority: GB
Inventors: Mielenz Holger; Heigele Christian
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2012-08-10
Filing date: 2013-08-08
Publication date: 2019-08-14
Anticipated expiration: 2033-08-08
Also published as: GB2507152A; FR2994486A1; GB201314268D0; FR2994486B1; DE102012214307A1

Description

Title

Process and apparatus for modelling an ambient field

State of the art

The present invention relates to a process and an apparatusfor modelling an ambient field, the extent of which isunknown, which has been detected by arbitrary sensorics.

In particular, the present invention relates to theautomobile ambient field, since it is often advantageoushere to create ambient-field maps of the environment,whereby items of information about the environment areobtained by means of sensors that are used in the vehicle.

The processes currently available for representing anambient field can, in principle, be divided up into twocategories. On the one hand, a mapping with the aid oftree structures, and, on the other hand, a mapping with theaid of discrete . cells arranged in a grid which isfrequently uniform.

In the case of the tree structures, each node of the treemaps a defined two-dimensional or three-dimensional spaceand may possess occupancy information about this space.Additionally, each node offers the possibility of sub-nodesif the territory that this node describes can be, or is to - be, described in more detailed manner. The same applies toeach sub-node. Accordingly, starting from a centralprincipal node, the complete space that this node describescan be mapped arbitrarily finely. If measured data,pertaining to regions outside the principal node are available, either these data can be discarded oralternatively a new principal node is created that covers amore far-reaching space than the principal node previouslyavailable, and the previous principal node, and optionallyfurther principal nodes, is/are subordinated, to the newprincipal node.

In the case of the grid-based processes, most commonly atwo-dimensional or three-dimensional space, limited to adefined extent, is described by a usually uniformrasterisation. Each of these cells contains a measure ofoccupancy (frequently a probability of occupancy) andoptionally further information (such as, for example,altitude or traversability). Such cells may also contain alist of items of altitude information stacked on top of oneanother, in order to reproduce compressed 3D information in .a 2D map.

Known, moreover, from the state of the art is printedpublication DE 10 2008 036 009 Al, which describes aprocess for protecting a vehicle against a collision. Forthis purpose, sensors have been fitted to the vehicle,which register the ambient field of the vehicle and enter 'the data acquired in this way into.an ambient-field map,the ambient-field map having been realised as a grid-basedmap. The grid points therein have been arrangedequidistantly and can assume the values "vacant","occupied" or "unknown", so that a discretised model of theenvironment arises.

Similarly, from DE 10 2010 013 093 Al a process is knownwhich enters obstacles in the environment of a vehicle intoa cell-based map. Overall, however, the cell-based and grid-based processes predominantly have the drawback thathere always a two-dimensional or three-dimensional spacelimited to defined tolerances is available by way ofambient-field map, into which the data acquired withrespect to existing obstacles are entered.

Moreover, the space has most commonly been uniformlydiscretised and can consequently store occupancy values oroccupancy probabilities at the discrete points. Thereforethe processes described above are very inaccurate preciselyin.the marginal regions of the discretised space, sincemeasured values that relate to regions outside thediscretised space are discarded. Moreover, no flexibilityis guaranteed, since the discretised space cannot beextended, so that in the event of the necessity to have tomap a larger region the entire discretised space always hasto be discarded, and a new, larger discretised space has tobe created.

Disclosure of the invention

The process according to the invention uses a linking of . individual cells, whereby the scope of the linked cells canbe extended or restricted in arbitrary manner. Therefore,the process is very flexible and can. preferably also beemployed where computing resources are available only to a .limited degree.

In accordance with the invention, at least one cell isprovided which includes the following features. Firstly,an identification is present with which the cell can beaddressed. The identification in this connection is uniqueamong all existing cells. Moreover, the cell contains neighbourhood relationships, whereby for each direction inwhich a further cell may be located the aforementionedidentification of the adjacent cell has been stored. Incase no adjacent cell were to be present in one direction,this has likewise been stored. Overall, it can thereforebe established whether further cells are located at theadjacent positions of a cell or whether the boundary of themodelled ambient field has been reached here. Finally,items of occupancy information are available in each cell,which have been realised by a spatial discretisation of thecell. The discretisation of all existing cells maypreferably be identical, whereby, in similarly preferablemanner, cells may also be discretised variably. Moreover,the discretisation may vary preferably within the cell ormay alternatively also preferably be uniform over the cell.At each discrete point of a cell an occupancy value or anoccupancy probability is stored. In this way, obstacles in.the environment can be modelled.

With the provision of at least one cell, it is possible tocreate an ambient-field .map of an object. For thispurpose, firstly a discrete object position within the atleast one cell has to be determined. This corresponds to aposition that represents the current location of the objectin the ambient-field map. In the course of a firstinitialisation of the ambient-field map, corresponding to afirst-time provision of at least one.cell, the discreteobject position is preferably freely defined. After this,the environment of the object is examined for obstacles,and in the event of an obstacle being present the positionthereof is determined. Subsequently the position of theobstacle is- transformed into a discrete obstacle position, so that within the cells which have been provided a discrete position is determined that corresponds to thereal position of the obstacle. For the purpose ofmodelling the obstacle, the occupancy value at the discreteobstacle position is changed in such a manner that, as aresult, the existence of an obstacle is indicated. /

Lastly, in accordance with the invention it is establishedwhether discrete intermediate positions are located betweenthe discrete obstacle position and the discrete objectposition. Since a detection of an obstacle normallypresupposes that the region between object and obstacle isvacant, in the case of the existence of at least onediscrete intermediate position the occupancy information atthe at least one discrete intermediate position is set to avalue that indicates that this point is vacant. Theoccupancy information has preferably been designed relativeto the previous occupancy information at the same discreteintermediate position, so that by means of the new valuefor the occupancy information it is indicated that thepoint is freer than previously assumed.

It is, moreover, preferably possible that a cell is able tostore further data besides the items of information thathave been described. This may be, for example, a value forthe clearance height at a defined point, or. a value for thetraversability of the undersurface. Accordingly, each cellcan be adapted to the currently prevailing environment, bycharacteristic data pertaining to the environment beingincorporated into the modelling.

The invention relates, moreover, to an apparatus formodelling an ambient field of an object. In accordancewith the invention, the apparatus includes a storage device which has preferably been set up to store one or more ofthe aforementioned cells. Moreover, the apparatus includesan environment sensor for detecting obstacles in theenvironment of the object. This sensor may be, forexample, a camera system, an ultrasonic sensor, a radarsensor or a lidar sensor. With the environment sensor itis preferably possible to determine both the presence of anobstacle and the spacing of an obstacle from the object.Finally, the apparatus includes a control unit which hasbeen connected both to the storage device and to theenvironment sensor. In accordance with the invention, thecontrol device has been set up in such a manner that saiddevice, implements the aforementioned process according tothe invention.

The process according to the invention and the apparatusaccording to the invention exhibit several advantages incomparison with the state of the art.

By virtue of the iterative linking and creation of thecells, the process is very compact. Only that space, aboutwhich items of environmental information are actuallyavailable, is described. A large discretised space, as inthe state of the art, is not necessary.

Since the local environment is described contiguously inthe storage device, the control unit with the storagedevice is able to calculate highly efficiently. Thetolerances of the ambient field have no influence on this. ·Solely the jumps from one cell to a further cell maynecessitate jumps within the storage device.

If a situation analysis exists, interesting regions of theenvironment can be determined, and the associated cells canbe created with a finer discretisation. For example,especially for narrow alleyways or parking spaces a finediscretisation is advisable, whereas for main roads acoarser discretisation is sufficient.

The dependent claims show preferred further developments ofthe invention.

In an advantageous manner the process according to theinvention is executed by the following steps beingfollowed. Firstly, from all existing cells an initial cellis selected which in at least one direction exhibits noneighbourhood relationship. Preferably, by way of initialcell that cell can, for example, be chosen within which thediscrete object position is located. After this, a furthercell is generated, this procedure involving the following-steps. By way of first step, an identification of thefurther cell is defined, whereby the identification, aboveall in the light of the cells already generated orprovided, is unique. and relates exclusively to the furthercell. Subsequently the neighbourhood conditions can bestored. This includes, on the one hand, a storing of theidentification of the further cell by way of neighbourhoodrelationship in the initial cell, and a storing of theidentification of the initial cell by way of- neighbourhoodrelationship in the further cell. In this way, the initialcell and the further cell have been locally linked to oneanother, so that a referencing is possible not globally butrather merely starting from an adjacent cell. Lastly,items of occupancy information that are formed by a spatialdiscretisation of the further cell are provided in the 1 further cell. At each discrete point in this connection adiscrete occupancy value or an occupancy probability hasbeen provided.

By virtue of the neighbourhood relationships, based merelyon the adjacent cells, the mapping of multi-levelsituations is also possible without difficulty. Forexample, ramps in multi-storey car parks do not have to bedetected specially as such but result automatically in anew generated cell with appropriate neighbourhoodconditions.

With the generating of a further cell, it is -possible toextend the ambient-field map of the object. For thispurpose, once again a discrete object position isdetermined within one of the cells which have been providedor generated. Subsequently the environment of the objectis examined further for obstacles, and in the event of anobstacle being present the position thereof is determined.Then the position of the obstacle is transformed into adiscrete obstacle position, so that within the cells whichhave been provided or generated a discrete position isdetermined that corresponds to the real position of theobstacle. For the purpose of modelling the obstacle, theoccupancy value at the discrete obstacle position ischanged in such a manner that, as a result, the existenceof an obstacle is indicated. Lastly, in accordance withthe invention it is established'whether discreteintermediate positions are located between the discreteobstacle position and the discrete object position. In theevent of the existence of at least one discreteintermediate position, the occupancy information at the at least one discrete intermediate position is set to a valuethat indicates that this point is vacant.

Overall, this preferred embodiment makes it possible toextend the modelling region of the ambient-field map veryeasily. This is a great advantage in comparison with thestate.of the art, since here an extension of the modellingregidn is not possible, or is possible only with greateffort.

In this connection it is particularly advantageous to applythe described preferred embodiment of the process accordingto the invention merely when a discrete obstacle positionin the existing cells - that is to say, in the cells whichhave been provided and/or generated - cannot be determined.Only in this case is it advantageous to generate a furthercell, in order to enlarge the entire modelling region. Itcan then preferably be examined once again whether adiscrete obstacle position in the enlarged modelling regioncan be determined.

Another advantageous embodiment of the process according tothe invention comprises the executing of the followingsteps. Precisely one cell is provided, which is designatedas the master cell. Consequently a discrete objectposition within the master cell is also defined. Lastly aspatial discretisation is defined, with which the items ofenvironmental information are to be stored. With thesesteps, the generating of an ambient-field map with a singlecell·, the master cell, is initialised. Should furthercells be required, these are inserted on demand. Thememory needed is therefore restricted to a minimum.

Moreover, there is preferably provision that the occupancyvalue can assume the values "occupied", "vacant" and . "unknown". The occupancy probability can preferably bespecified with a value between 0 and 1, where 0 preferablycorresponds to "vacant", 0.5 preferably corresponds to"unknown", and 1 preferably corresponds to "occupied".

This enables a comprehensive describing of the environmentof the object within the cells.

In particularly preferred manner there is provision thatfor each cell a number of items of occupancy informationare determined, whereby only items of occupancy informationthat do not contain the value "unknown" are taken intoaccount. Should this number fall below a first value, thecorresponding cell is deleted. By virtue of the deletingof cells with only little information content, storagespace, can be conserved, since it can be assumed that a cellwith little information content does not play an importantrole in the modelling of the ambient field. The firstvalue is preferably dependent on the discretisation of thecell, so that in the case of fine discretisation the firstvalue is higher" than in the case of coarse discretisation.

In advantageous manner the process according to theinvention is implemented by the cells being regarded asrectangular. In particular, it is advantageous if thecells are regarded as square. In this case, an environmentto be modelled can be mapped very easily by means of thecells. In addition, merely four neighbourhood conditionshave to be dealt with.

Moreover, there is preferably provision that the cells allexhibit the same size. This simplifies the process according to the invention, since all the cells can betreated identically. Alternatively, there is preferablyprovision that the cells exhibit differing sizes. Hencedistricts having different regions of varying size, forexample, can be imaged more easily.

In addition, the cells may preferably represent a two-dimensional space or even a three-dimensional space.Depending on the type of object, the environment of whichis being modelled, the one or other type is advantageous.For a land-based vehicle, a use of two-dimensional cells,for example, is. sufficient.

In an advantageous embodiment of the process according tothe invention the following steps are additionallyexecuted. Firstly, an absolute position of each cellwithin a fixed coordinate system is determined. This isdone with the aid of the neighbourhood relationships, sothat the relative data of the neighbourhood relationshipsare converted into absolute data within the fixedcoordinate system. Subsequently it is determined whichcells have been placed at an identical point within thecoordinate system. Such a situation may occur if aposition within a first cell is approached by two differentadjacent cells. Since the adjacent cells possess noinformation whatsoever as to whether the respective othercell has already generated the first cell, at any rate anew first cell is generated. Consequently two first cellsare present which, however, exhibit the same content.Therefore for the case where two' cells exhibit the sameabsolute position the items of occupancy information arecompared. Should the items of occupancy information of thecells intersect, or should the items of occupancy information be identical, it is to be assumed that bothcells are modelling the same territory. For this reason,in a concluding step the cells with identical or partlyidentical items of occupancy information are merged to forma single cell.

In a preferred embodiment of the apparatus according to theinvention the storage device has. been set up to return,upon a request for a new cell by the control unit, theidentification of a first cell from a first number of cellswithout occupancy information and neighbourhood -relationships. Hence it is possible to accelerate theprocess of generating a cell, since here no physicalstorage space has to be requested, but rather use is madeof a cell from a stock of empty cells. Therefore there ispreferably provision that the storage device always storesa second number of cells without occupancy information and . neighbourhood relationships. The second number of cells inthis case is preferably at least just as large as the firstnumber of cells. Consequently a stock of cells is alwaysavailable, in which connection the time-consuming processof requesting storage space has been decoupled from theprocess of generating the cell.

Brief description of the drawing

Exemplary embodiments of the invention will be described indetail in the following with reference to the accompanyingdrawing. In the drawing:

Figure 1 is a schematic view of a cell such as is usedin the process according to the inventionaccording to a preferred embodiment,

Figure 2 is a schematic view of two cells with which theambient field of a vehicle is modelled with theprocess according to the invention according tothe preferred embodiment,

Figure 3 is a schematic view of a real environment whichis modelled with the process according to theinvention according to the preferredembodiment,

Figure 4 is a schematic, planar view of several cellswhich were generated with the process accordingto the invention according to the preferredembodiment,

Figure 5 is a schematic, spatial view of several cellswhich were generated with the process accordingto the invention according to the preferredembodiment, and

Figure 6 is a schematic overview of the apparatusaccording to a preferred embodiment of theinvention.

Embodiments of the invention

Figure 1 shows a first cell 1 which is used for modellingan environment of an object. The first cell 1 exhibits atotal of four neighbourhood relationships which divide upinto a first direction 11, a second direction 12, a thirddirection 13 and a fourth direction 14. Consequently it is possible, starting from the first cell 1, to generate four further cells. The first cell 1 has been discretised andcan receive items of occupancy information at discretepoints 10. These items of occupancy information havefirstly been pre-allocated with the value "unknown".

In Figures 2 and 3 it has been illustrated how the cellsare used in order to model the environment of a vehicle 4.In this connection, Figure 2 represents the modelled stateby means of a first cell 1 and a second cell 2, whereasFigure 3 sketches the real environment from a bird's-eyeview. With a view to better clarification, the regionsthat are modelled by the first cell 1 and the second cell 2have also been sketched in Figure 3. Within the first cellla discrete object position 40 is determined whichcoincides with the real position of the vehicle 4. Asshown in Figure 3, the vehicle 4 is driving alongside anobstacle 3. Ambient-field sensors 5 built into the vehicleregister the obstacle 3, so that the latter can berepresented in the first cell 1 at the discrete obstaclepositions 32. For this purpose, a notional laser beam, forexample, is shone between discrete object position 40 andeach discrete obstacle position 32, and the items ofoccupancy information along the laser beam are set to"vacant". At the end of the beam - that is to say, at thediscrete obstacle positions 32 - the occupancy informationis changed to "occupied". However, as soon- as the vehicle4 approaches the boundaries of the region that can bemodelled with the first cell 1 the problem arises that adiscrete obstacle position 31 is situated outside the cell1 and consequently cannot be represented. For this reason,a second cell 2 is generated in the second direction 12 ofthe first cell 1, so that a neighbourhood relationshipexists between the first cell 1 and the second cell 2.

With successful generation of the second cell 2,consequently discrete obstacle position 31 can also bemodelled.

The generating of new cells is always executed on the basisof a cell that is already present. Accordingly, in

Figure 4 an example has been represented of how, startingfrom the first cell 1, a total of three further cells aregenerated: the second cell 2, a third cell 6 and a fourthcell 7. In this connection the neighbourhood relationshipof the first cell 1 in the second direction 12 is identicalto the neighbourhood relationship of the second cell 2 inthe fourth direction 24. Consequently a transition fromthe first cell 1 to the second cell 2 is present here. Thesame applies to the neighbourhood relationships of thesecond cell 2 relative to the third cell 6 in the thirddirection 23 of the second cell 2 and in the firstdirection 61 of the third cell 6, and also to theneighbourhood relationships of the third cell 6 relative tothe fourth cell 7 in the fourth direction 64 of the thirdcell 6 and in the second direction 72 of the fourth cell 7.However, there is no neighbourhood relationship between thefirst cell 1 and the fourth cell 7. Should the vehicle 4,starting from a location in the fourth cell 7, move in thedirection of the first cell - that is to say, in the firstdirection 71 of the fourth cell 7 - a new cell would becreated which would be situated. absolutely at the sameposition as the first cell 1. The same also applies to thethird direction 13 of the first cell 1.

The advantage of the local neighbourhood relationships .within the cells has been elucidated in Figure 5. In thiscase, the vehicle 4 is driving up a helical tower, as may be the case, for example, in multi-storey car parks.Starting from the first cell 1, firstly several cells aregenerated in the second direction 12 of the first cell 1until finally a fifth cell 8 is obtained. Starting fromthe fifth cell 8, a further cell 9 is generated which issituated absolutely at the same position as the first cell1, but at a higher level. This is automatically taken intoaccount with the process according to the invention, sincethe further cell 9 is generated on the basis of the fifthcell 8 in the third direction 83 of the fifth cell 8.Consequently the neighbourhood relationship of the fifthcell 8 in the third direction 83 points not towards thefirst cell 1 but rather to the further cell 9. Similarly,the neighbourhood relationship of the first cell 1 in thefirst direction 11 also does not point to the fifth cell 8'located at the same absolute position..

In principle, however, the case could also occur that thefirst cell 1 and the further cell 9 describe the samespace, for example because the object 4 has moved in acircular-arc trajectory on one level. Therefore in anadditional step it is examined whether cells are presentthat have to be merged. This is done by the absoluteposition of each of the generated cells being ascertained.Consequently it can be established that the first cell 1and the further cell 9 exhibit the same absolute position.Subsequent to this, it is examined whether the cellslocated at the same absolute position describe the samecontent. For this purpose the items of occupancy . information are compared, and in the event of a limitingvalue of a measure of the similarity of the items ofoccupancy information being exceeded the items of occupancyinformation and the neighbourhood relationships of the two cells are merged in one of the cells, the cell no longerrequired being deleted.

In Figure 6 the apparatus according to the invention formodelling an environment has been represented. Saidapparatus includes a storage device 200 which has been setup to store a plurality of cells. Connected to the storagedevice'200 is a control device 100 which is likewiseconnected to the environment sensor 5.

The control device 100 can therefore provide and generatecells which are subsequently stored into the storage device200. By means of the environment sensor 5 the controldevice 100 scans the environment to be modelled forobstacles, and in this way determines the existence ofobstacles 3 as well as the discrete obstacle positions 31,32 within the cells which have been generated or provided.

Moreover, the control device 100 is able to realise themodelling of an ambient field also with limited storagespace. In this case a number of cells that may be usedmaximally is defined. As soon as this number has been . attained, in the case of a further cell which is requiredthe cell that was first set up is deleted, and consequentlystorage space is freed for a further cell. The modeltherefore encompasses merely the most recent part of theenvironment, but in exchange it manages with limitedstorage space.

In addition, the storage device 200 may be bipartite, onepart having been designed as archive with long access-time,and a further part having been designed as operationalmemory with short access-time. Consequently the deleting of cells described in the preceding section may alsorepresent a relocating out of the operational memory into·the archive, so'that a cell from the archive is restored inthe case of a return of the object 4 into an environmentthat corresponds to a part of the model already archived.

Claims

1. Process for modelling an ambient field of an object (4), in particular of a vehicle, comprising the followingsteps : providing at least one cell (1, 2, 6, 7, 8, 9) having a unique identification, neighbourhood relationships which for eachdirection (11, 12, 13, 14) in which further cells(1, 2, 6, 7, 8, 9) may be located include anidentification of an existing adjacent cell or anitem of information to the effect that no adjacentcell is present in this direction, and items of occupancy information that are formed by aspatial discretisation of the cell (1), whereby ateach discrete point (10) a discrete occupancy valueor an occupancy probability has been specified,determining a discrete object position (40) in the atleast one cell (1, 2, 6, 7, 8, 9) which represents thecurrent position of the object (4), detecting an obstacle (3) in the environment of theobject (4) and determining the position of the obstacle(3) , determining at least one discrete obstacle position(31, 32) in one of the cells (1, 2, 6, 7, 8, 9) whichhave been provided that corresponds to the position ofthe obstacle (3), changing the occupancy value or the occupancyprobability of the at least one discrete obstacleposition (31, 32) in such a manner that the presence ofthe obstacle (3) is indicated, and changing at least one discrete intermediate position inat least one of the cells (1, 2, 6, 7, 8, 9) which havebeen provided between discrete obstacle position (31,32) and discrete object position (40) in such a mannerthat these positions indicate a vacant environment in case at least one such discrete intermediate positionis present.

2. Process according to Claim 1, comprising the following steps: defining an initial cell from the existing cells (1, 2,6, 7, 8, 9) that exhibits no adjacent cell (1, 2, 6, 7,8, 9) at least in one vacant direction (11, 12, 13, 14) , generating a further cell (1, 2, 6, 7, 8, 9) having the same features as the at least one cell (1, 2, 6, 7, 8, 9) which has been provided, comprising the followingsteps : defining an identification of the further cell (1,2, 6, 7, 8, 9), storing the identification of the further cell (1,2, 6, 7, 8, 9) in the initial cell by way ofneighbourhood relationship in the vacant direction(11, 12, 13, 14), defining a further direction in which the initialcell is situated, viewed from the further cell (1,2, 6, 7, 8, 9), storing the identification of the initial cell inthe further cell (1, 2, 6, 7, 8, 9) by way ofneighbourhood relationship in the furtherdirection, and providing items of occupancy information of thefurther cell (1, 2, 6, 7, 8, 9) that are formed bya spatial discretisation of the further cell (1, 2,6, 7, 8, 9), whereby at each discrete point (10) adiscrete occupancy value or an occupancyprobability has been specified, determining a discrete object position (40) within oneof the cells (1, 2, 6, 7, 8, 9) which have beengenerated or within one of the cells (1, 2, 6, 7, 8, 9) which have been provided that represents the currentposition of the object (4), detecting an obstacle (3) in the environment of theobject (4) and determining the position of the obstacle(3) ,determining at least one discrete obstacle position(31, 32) within one of the cells (1, 2, 6, 7, 8, 9)which have been generated or within one of the cells (1, 2, 6, 7, 8, 9) which have been provided thatcorresponds to the position of the obstacle (3),changing the occupancy value or the occupancyprobability of the at least one discrete obstacleposition (31, 32) in such a manner that the presence ofthe obstacle (3) is indicated, and changing at least one discrete intermediate position inat least one of the cells (1, 2, 6, 7, 8, 9) which havebeen provided and/or of the cells (1, 2, 6, 7, 8, 9)which have been generated between discrete obstacleposition (31, 32) and discrete object position (40) insuch a manner that these positions indicate a vacantenvironment in case at least one such intermediateposition is present.

3. Process according to Claim 2, wherein the stepsaccording to Claim 2 are implemented only when a discreteobstacle position (31, 32) in one of the cells (1, 2, 6, 7,8, 9) which have been provided or in one of the cells (1,2, 6, 7, 8, 9) which have been generated cannot bedetermined.

4. Process according to one of the preceding claims,comprising the following steps: providing precisely one cell (1, 2, 6, 7, 8, 9) whichis designated as the master cell, defining a discrete object position (40) within themaster cell that corresponds to a current position ofthe object (4), and defining a spatial discretisation, within which theitems of occupancy information are to be represented.

5. Process according to one of the preceding claims,wherein the occupancy value encompasses the values"occupied", "vacant" and "unknown", and/or the occupancyprobability is specified as a value between 0 and 1, where 0 corresponds to the value "vacant", 0.5 corresponds to thevalue "unknown", and 1 corresponds to the value "occupied".

6. Process according to Claim 5, comprising thefollowing steps: determining a number of items of occupancy informationfor each cell (1, 2, 6, 7, 8, 9) that do not containthe value "unknown", deleting a cell (1, 2, 6, 7, 8, 9) in which the number of items of occupancy information falls below a firstvalue .

7. Process according to one of the preceding claims, wherein each cell (1, 2, 6, 7, 8, 9) exhibits a rectangular shape, in particular a square shape.

8. Process according to one of the preceding claims,wherein all the cells (1, 2, 6, 7, 8, 9) exhibit the samesize or the cells (1, 2, 6, 7, 8, 9) exhibit differingsizes .

9. Process according to one of the preceding claims,wherein each cell (1, 2, 6, 7, 8, 9) represents theenvironment two-dimensionally or three-dimensionally.

10. Process according to one of the preceding claims,comprising the following steps: determining an absolute position of each cell (1, 2, 6, 7, 8, 9) within a fixed coordinate system on the basisof the neighbourhood relationships, determining a group of cells (1, 2, 6, 7, 8, 9) thatare situated at the same absolute position, comparison of the items of occupancy information of, ineach instance, two cells (1, 2, 6, 7, 8, 9) from thegroup of cells, merging the two cells (1, 2, 6, 7, 8, 9) from the groupof cells to form one cell in case the items ofoccupancy information of the two cells are at leastpartly identical.

11. A process, for modelling an ambient field of an object,substantially as herein described with reference to theattached drawings.

12. Apparatus for modelling an ambient field of anobject (4), in particular of a vehicle, comprising a storage device (200), at least one environment sensor (5) for detectingobstacles (3) in the environment of the object (4), anda control unit (100) which has been connected to thestorage device (200) and to the environment sensor (5),wherein the control unit (100) executes a process according toone of Claims 1 to 11, and the cells (1, 2, 6, 7, 8, 9) are stored within thestorage device.

13. Apparatus according to Claim 13, wherein the storage device (200) has been set up to return,upon request for a new cell (1, 2, 6, 7, 8, 9) by thecontrol unit (100), the identification of a cell (1, 2, 6, 7, 8, 9) from a first number of cells (1, 2, 6, 7, 8, 9) without occupancy information and neighbourhoodrelationships, the storage device (200) has been set up to storealways a second number of cells (1, 2, 6, 7, 8, 9)without occupancy information and neighbourhoodrelationships, and the second number of cells (1, 2, 6, 7, 8, 9) is atleast just as large as the first number of cells (1, 2,6, 7, 8, 9) .