Method of assisting detection of man-made structures in a digital elevation map (DEM)

{
  "publication_number": "US6104981A",
  "country": "US",
  "kind": "A",
  "title": "Method of assisting detection of man-made structures in a digital elevation map (DEM)",
  "abstract": "A method of detecting man-made structures in a digital representation of a terrain, wherein said representation is a digital elevation map, and wherein said method comprises the following steps: computing isolines in said digital elevation map; filtering said isolines on the basis of a size criterion; computing extremum isolines from the isolines filtered during the preceding step; and determining said regions of interest. The invention is applicable to any process involving supervision of a geographical site (e.g. planning cellular telecommunications networks).",
  "claims": [
    "1. A method of detecting regions of interest containing man-made structures in a terrain representation, wherein said terrain representation is a digital elevation map, and wherein said method comprises: providing information representing the digital elevation map and information representing a size criterion; using a computer to compute isolines in said provided digital elevation map; filtering said computed isolines on the basis of the provided size criterion; computing extremum isolines from the filtered isolines; and isolating said regions of interest containing man-made structures from regions delimited by the computed extremum isolines.",
    "2. A method according to claim 1, wherein, after computing said extremum isolines, said method includes: inputting a threshold value; computing a total length of ridge lines contained in each of said extremum isolines; and filtering said extremum isolines as a function of a comparison between said computed total length of ridge lines and said inputted threshold value.",
    "3. A method according to claim 1, wherein each region of interest is delimited in three dimensions: by an isoline resulting from the computed extremum isolines; by the horizontal plane containing said extremum isoline; and by the horizontal plane containing the point of maximum height contained in said isoline.",
    "4. A method according to claim 1, wherein computing the isolines is immediately followed by deleting the open isolines from said isolines.",
    "5. A method according to claim 2, wherein each region of interest is delimited in three dimensions: by an isoline resulting from the filtered extremum isolines; by the horizontal plane containing said extremum isoline; and by the horizontal plane containing the point of maximum height contained in said isoline.",
    "6. A method of optimizing locations of base stations for cellular radiocommunications networks involving detecting regions of interest containing man-made structures in a terrain representation, wherein said terrain representation is a digital elevation map, and wherein said method comprises: providing information representing the digital elevation map and information representing a size criterion; using a computer to compute isolines in said provided digital elevation map; filtering said computed isolines on the basis of the provided size criterion; computing extremum isolines from the filtered isolines; and isolating said regions of interest containing man-made structures from regions delimited by the computed extremum isolines.",
    "7. A method according to claim 6, wherein, after computing said extremum isolines, said method includes: inputting a threshold value; computing a total length of ridge lines contained in each of said extremum isolines; and filtering said extremum isolines as a function of a comparison between said computed total length of ridge lines and said inputted threshold value.",
    "8. A method according to claim 6, wherein each region of interest is delimited in three dimensions: by an isoline resulting from the computed extremum isolines; by the horizontal plane containing said extremum isoline; and by the horizontal plane containing the point of maximum height contained in said isoline.",
    "9. A method according to claim 6, wherein said computing the isolines is immediately followed by deleting the open isolines from said isolines.",
    "10. A method according to claim 7, wherein each region of interest is delimited in three dimensions: by an isoline resulting from the filtered extremum isolines; by the horizontal plane containing said extremum isoline; and by the horizontal plane containing the point of maximum height contained in said isoline."
  ],
  "description_excerpt": "The present invention relates to a method of assisting detection of man-made structures in a Digital Elevation Map (DEM).\n\nThe problem of detecting man-made structures in a computerized representation (image, digital elevation map, etc.) occurs in numerous applications, e.g. in planning cellular radiocommunications networks.\n\nSuch a network, e.g. a GSM (Global System for Mobile communications) network includes a plurality of base stations distributed geographically. Each of the stations serves to offer radio coverage for a determined geographical zone referred to as a \"cell\".\n\nThe geographical zone that any given base station actually covers depends on the geographical environment, and in particular on the presence of man-made structures in that environment. Thus, in order to locate the base stations in optimum manner, i.e. so that a mobile station is always able to communicate with a base station, it is necessary to know the positions of such man-made structures.\n\nConventionally, such terrain analysis is performed on the basis of aerial photographs or satellite photographs, either manually or by means of detection assistance tools.\n\nSuch image processing tools make it possible to differentiate between a plurality of regions in an image by analyzing and classifying textures, certain regions containing, for example, a high density of buildings, and others having a low density.\n\nBut the drawbacks of such an approach quickly become apparent:\n\nThat method does not make it possible to isolate the buildings and can only show up zones. For application to cellular network planning, such an approach is inadequate.",
  "cpc": [
    "G06T 17/05"
  ],
  "ipc": [
    "G06K 9/00",
    "G06T 17/05"
  ],
  "assignees": [
    "Alcatel SA"
  ],
  "inventors": [
    "Christian Louis",
    "Yves Lechervy"
  ],
  "filing_date": "1998-02-19",
  "publication_date": "2000-08-15",
  "grant_date": "2000-08-15",
  "priority_date": "1997-02-20",
  "application_number": "US-2581798-A",
  "family_id": "9503968",
  "cited_by_count": 23,
  "citations": [
    "US5444618A",
    "US5839090A"
  ]
}