Method of sampling a terrain data base

• US 5,630,035 A
• Filed: 01/18/1994
• Issued: 05/13/1997
• Est. Priority Date: 01/18/1994
• Status: Expired due to Term

• Current Assignee: Honeywell Incorporated (Honeywell International Inc.)
• Original Assignee: Honeywell Incorporated (Honeywell International Inc.)
• Inventors: Thorpe, Douglas E., Gjullin, Robert M.
• Primary Examiner(s): Zimmerman, Mark K.
• Assistant Examiner(s): Burwell, Joseph R.
• Application Number:
  US08/183,533
• Time in Patent Office: 1,211 Days
• Field of Search: 395/121, 395/123, 395/125, 395/127, 395/130, 364/443, 364/423, 364/458, 340/988, 340/995
• US Class Current: 345/427
• CPC Class Codes: G06T 15/20 Perspective computation
• CPC Class Codes: G06T 17/05 Geographic models
• CPC Class Codes: G06T 2200/28 involving image processing hardware

Abstract

A convergence model is shown and described for accommodating variation in data post spacing in a digital terrain elevation database (DTED) based on longitude and latitude address values for data posts. Under such a database structure, data posts lying along lines of latitude vary in spacing according to latitude, and converge at the poles with zero spacing therebetween. To scan a circular region of data posts relative to a given data post, e.g., a threat installation, this variation in data post spacing is considered by appropriately scaling sample step spacing along radials traversed in executing a radial spoke scan pattern. In this manner, a circular region of data posts surrounding a given data post may be sampled using simple, dedicated hardware despite this variation in data post spacing.

Claims

1. A method of providing intervisibility calculations for known terrain using a computer comprising the steps of:

providing a digital terrain elevation data (DTED) database which models the known terrain and has data posts corresponding to points on the known terrain, the data posts being individually addressable in X and Y dimensions wherein spacing between adjacent terrain points varies as a function of at least one of said X and Y dimensions;

identifying a threat data post by X and Y dimension values;

identifying a set of radials of length corresponding to said constant radius and emanating from said threat data post;

dividing said at least one of said X and Y dimensions into a plurality of sub-zones and for each sub-zone identifying a data post spacing value in said X and Y dimensions corresponding to terrain point spacing therein;

traversing at least one of said radials by identifying a plurality of delta X and delta Y value pairs based on an angular orientation of said at least one radial, said plurality of delta X and delta Y value pairs are scaled according to said plurality of sub-zones, further identifying a given delta X and delta Y value pair from said plurality of sub-zones according to said threat post X and Y dimension values, and successively sampling along said at least one radial by successively accumulating said given delta X and delta Y values to identify successive sample points along said at least one radial whereby sampling at a given number of said successive sample points provides sampling along said at least one radial to said given length; and

calculating intervisibility of the sample points with respect the threat point.

2. A method of providing intervisibility calculations for known terrain using a computer comprising the steps of:

providing a digital terrain elevation data (DTED) database which models the known terrain and has data posts corresponding to points on the known terrain, where the DTED database has data posts addressable in X and Y dimensions, each data post corresponding to the points on the known terrain, spacing between adjacent terrain points in the X dimension being variable as a function of the Y dimension of the adjacent data posts;

identifying an X dimension terrain point spacing for each of a plurality of X dimension sub-zones;

maintaining a table of delta X and delta Y value pairs, said table grouping said delta value pairs according to a plurality of given angular orientations, each group of delta value pairs corresponding to one of said angular orientation, each member of each group corresponding to one of said sub-zones;

selecting a threat data post having both a threat X address value and a threat Y address value;

selecting at least one radial emanating from said threat data post and defining a given angular orientation;

selecting a delta value pair as a function of said given angular orientation and said threat Y address value, where said threat Y address value corresponds to one of said sub-zones;

sampling along said at least one radial at a given number of sample points by successive accumulation of delta X and delta Y values of said selected delta value pairs whereby sampling occurs along said at least one radial; and

calculating intervisibility of the sample points with respect the threat point.

3. A method according to claim 2 wherein said X dimension terrain point spacing for each of a plurality of X dimension sub-zones is a function of data post spacing at the center of each sub-zone.