What exactly is a topography?
Topography is the study of the three dimensional features and forms of the Earth surface and it is used to describe the changes in elevation in a particular area.
DEMs: A Digital Elevation Model (DEM) is a 3D representation of the earth’s topographic surface, created from elevation data. It shows the height of land features relative to sea level, excluding surface features (buildings, vegetation, etc.). DEMs are represented as a grid where each cell contains an elevation value. Image: (source: esri website)
Contour Lines: Contour lines represent the topography of areas by connecting features of equal elevation as lines. Contour lines are spaced at regular intervals representing a step change increase or decrease in the elevation. Closely spaced contour lines represent steep topographies while widely spaced contour lines represent gentle topographies.
Contour map (left), illustration of contour lines on a map (middle) and on a profile (right) [Source: Geo-libretexts]
How is the data collected?
Remote sensing: Elevation data can be collected using aerial platforms such as satellites (e.g. SRTM which provides low to medium resolution data with a 30-m resolution), drones, and aircraft. These platforms use various techniques to collect the spatial data including radar and LiDAR, with LiDAR offering higher resolution data ranging from ~0.5m to 2.5m.
Ground surveying: Traditional methods such as total stations, GPS and leveling are typically used for small areas which require higher accuracy.
What is the support of the data?
Point data: Discrete elevation points (e.g. Lidar point clouds, GPS data points)
Vector data: contour lines
Raster grid: Each pixel (or cell) contains an elevation value (DEM)
Surface: a mesh (TIN: triangular irregular network) of interconnected triangles where the vertices represent known elevation points
How is this data typically displayed in geoscientific software?
DEMs are imported into geoscientific softwares as geotiffs or grids and are converted to a raster (.ers). Topographic data can be viewed as contour maps, hillshade maps or 3D surface models.
What does it mean for geologists in terms of targeting mineral systems?
Topographic data can provide insights into identifying structures (faults, folds, etc.) and processes which could indicate the presence of mineral occurrences/deposits. Furthermore, topography influences the water flow direction, creating watersheds which in turn can control the soil or sediments composition.
How is this used in the VRIFY AI targeting workflow?
DEMs are used to add a z-dimension (elevation) to surface geochemistry data if it is not provided. DEMs are also used in preliminary feature engineering for materials that may have been transported (e.g., tills, soils, stream sediments). They are used to interpolate the surface geochemistry for these transported materials by producing their catchment areas.
Still have questions?
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