Soil and topography surveying
Methods of characterizing subsurface conditions in a selected geographic region previously associated as a whole with a specific subsurface material characteristic reference profile such as from a USDA-NRCS soil survey. The method includes deploying a sensing tool at selected positions within the geographic region to determine a depth-referenced subsurface material characteristic such as soil type or strata, comparing the determined subsurface material characteristic to the subsurface material characteristic reference profile associated with the geographic region to determine a correlation between the subsurface material characteristic reference profile and the depth-referenced subsurface material characteristic, and then deciding whether to deploy the tool at another position, and at what optimum position to deploy the tool, by considering the correlation.
1. A method of characterizing subsurface conditions in a selected geographic region previously associated as a whole with a specific subsurface material characteristic reference profile, the method comprising deploying a sensing tool at a selected position within the geographic region, the tool constructed to be responsive to a selected subsurface material attribute; determining, from a signal received from the deployed tool, a depth-referenced subsurface material characteristic at the selected position; comparing the determined subsurface material characteristic to the subsurface material characteristic reference profile associated with the geographic region to determine a correlation between the subsurface material characteristic reference profile and the depth-referenced subsurface material characteristic as determined from the signal received from the deployed tool; and then deploying the tool at another position within said geographic region by considering the correlation determined from said selected position.
2. The method of claim 1 wherein the geographic region corresponds to one bounded area of a patchwork of such bounded areas on a map, each bounded area having an associated subsurface material characteristic reference profile.
3. The method of claim 2 wherein the geographic region comprises an individual Soil Map Unit as outlined on an USDA-NRCS Soil Survey map and referenced to said subsurface material characteristic reference profile by the USDA-NRCS Soil Survey map.
4. The method of claim 1 wherein the depth-referenced subsurface material characteristic comprises a digital log of a soil property as a function of depth.
5. The method of claim 4 wherein comparing the determined subsurface material characteristic to the subsurface material reference characteristic profile associated with the geographic region includes comparing a soil layer boundary depth, as determined from the soil property log, with a reference layer boundary depth as determined from the subsurface material reference characteristic profile.
6. The method of claim 4 wherein the subsurface material reference characteristic profile comprises a digital reference profile log containing at least about 10 discrete, depth-referenced data points, said correlation comprising a computed numerical value indicative of degree of similarity between the digital soil property log and the digital reference profile log.
7. The method of claim 1 wherein comparing the determined subsurface material characteristic to the subsurface material reference characteristic profile associated with the geographic region includes comparing soil texture at a selected depth, as determined from the determined subsurface material characteristic, with a reference texture as determined from the subsurface material reference characteristic profile.
8. The method of claim 1 wherein deploying the tool includes penetrating soil with the tool to a depth of at least 6 inches.
9. The method of claim 1 wherein deploying the tool includes penetrating soil with the tool to a depth of at least 24 inches.
10. The method of claim 1 further comprising geo-referencing the selected position to a coordinate system with a Global Positioning System.
11. The method of claim 1 wherein the depth-referenced subsurface material characteristic comprises a log of data taken at multiple depths at the selected position.
12. The method of claim 1 wherein the tool is responsive to light reflected from adjacent subsurface material in situ, and wherein determining the depth-referenced subsurface material characteristic includes generating a depth-referenced, rastered image of the subsurface material.
13. The method of claim 12 comprising collecting and digitally processing a series of images of adjacent subsurface materials as the tool is forced through the subsurface materials.
14. The method of claim 1 further comprising traversing the geographic region while obtaining landscape position and elevation measurements; combining the position and elevation measurements to form a digital elevation model; adjusting a depth reference of the subsurface material characteristic determined at each of several test locations in accordance with the digital elevation model; and then combining the depth reference-adjusted subsurface material characteristics to form a three-dimensional subsurface model of the material characteristic.
15. The method of claim 1 wherein the depth-referenced subsurface material characteristic comprises multiple, discrete data points obtained at selected depths at the selected position.
16. The method of claim 15 wherein the selected depths are chosen to correspond to soil layers identified in the subsurface material characteristic reference profile associated with the geographic region.
17. The method of claim 15 wherein the discrete data points are spaced apart in elevation according to soil layer thickness included in the subsurface material characteristic reference profile.