Topographic data gathering method

• US 4,495,500 A
• Filed: 01/26/1982
• Issued: 01/22/1985
• Est. Priority Date: 01/26/1982
• Status: Expired due to Term

• Current Assignee: SRI International, Inc.
• Original Assignee: SRI International, Inc.
• Inventors: Vickers, Roger S.
• Primary Examiner(s): Gruber, Felix D.
• Assistant Examiner(s): Huang, Karl
• Application Number:
  US06/342,819
• Time in Patent Office: 1,092 Days
• Field of Search: 364/433, 364/434, 364/449, 364/450, 364/454, 364/460, 343/5 DP, 343/5 MM, 343/7 TA, 343/5 CM, 340/27 NA
• US Class Current: 342/59
• CPC Class Codes: G01S 13/89 for mapping or imaging

Abstract

A system for gathering topographic data for use in computer generation of topographic maps of various forms. This system includes equipment mounted in an aircraft which can be flown over a terrain area which is to be surveyed. The equipment comprises a low frequency radar which is capable of penetrating foliage in the survey area for generating a signal representative of the distance from the aircraft to the terrain surface, a precision altimeter that produces a signal representative of the altitude of the aircraft with respect to a reference plane such as sea level, temperature and humidity sensors for producing signals representative of those quantities, a clock for producing a signal representative of a standard time, and a digital recorder for recording the previously named signals which are produced during over flight of a survey area. The recorder has a recording medium which can be removed from the aircraft and employed at a remote time and place as computer input for effecting generation of topographic maps showing various characteristics of the survey area. Concurrent with the gathering of data in the aircraft, data representative of temperature and humidity at the surface of the survey area are gathered and recorded on a second recording medium. The two recording media can be combined at a remote time and place as computer input to produce highly accurate topographic maps.

The system can include a second radar operating at a different frequency from that at which the first mentioned radar operates. One of the radars can accurately penetrate the foliage and the other can measure the distance from the aircraft to the foliage surface so that information concerning the foliage can be generated. The system also includes circuitry for responding to surface water in the survey area so that accurate mapping of rivers, lakes, streams and swamps can be achieved.

Claims

1. A method for acquiring data for use in producing a computer generated topographic map of terrain comprising the steps of providing a radar, transporting a radar along a path above the terrain to generate plural distance signals indicative of the distance from the radar to the terrain surface at spaced apart points along the path, producing during said transporting step plural location coordinate signals representative of the locations of the points, generating during said transporting step plural altitude signals representative of the altitude of the radar at the points with respect to a reference plane, producing a continuous series of timing pulses recurring at preselected time intervals for affording correlation with the points along the path, simultaneously recording said distance signals, said coordinate signals, said altitude signals and timing pulses in real time on a recording medium, so that the signals recorded on the recording medium and the ground temperature and pressure signals can be inputted to a computer in time correlation for generation thereby of a topographic map.

2. A method of acquiring data for use in producing a computer generated topographic map of foliage covered terrain comprising the steps of providing a first radar operating at a first frequency low enough to penetrate the foliage and produce a return from the ground surface beneath the foliage, providing a second radar operating at a second frequency higher than the first frequency to produce a return from the surface of the foliage, transporting the first and second radars along a path above the terrain to generate a plurality of first signals indicative of the distance from the radars to the ground surface and a plurality of second signals representative of the distance from the radars to the foliage surface, producing during said transporting step plural location coordinate signals representative of the location of the radars along the path, generating during said transporting step a plurality of altitude signals representative of the altitude of the radars with respect to a reference plane, sensing the amplitude of the returns produced by the radars, producing a flag signal when the amplitude exceeds a preselected level that is indicative of a water surface on the terrain, and simultaneously recording said first, second, coordinate and altitude signals in real time on a recording medium so that the signals recorded on the recording medium can be imputted to a computer for generation thereby of a topographic map.

3. A method for acquiring data for use in producing a computer generated topographic map of foliage covered terrain comprising the steps of overflying the terrain along a flight path, directing at the terrain while traversing the flight path a first radar pulse at a first frequency and a second radar pulse at a second frequency that is greater than the first frequency so as to produce a plurality of first signals representative of the distance from points along the flight path to the terrain surface and a plurality of second signals representative of the distance from points along the flight path to the foliage surface, measuring the distance of the points along the flight path above a preselected reference plane to derive plural altitude signals, generating location coordinate signals representative of the location of the points along the flight path relative to the terrain, producing a continuous series of timing pulses recurring at preselected time intervals for affording correlation with the points along the path, simultaneously recording the first, second, altitude and coordinate signals and timing pulses on a recording medium measuring temperature and pressure on the terrain surface to produce a ground temperature signal and a ground pressure signal, and recording the ground temperature signal and the ground pressure signal with a standard time signal to afford subsequent input of the data on the recording medium and the ground temperature and pressure signals to a computer in time correlation for generation of a topographic map of the terrain.