5. Topography

The pycsamt.topo package embeds real station elevation into 2-D resistivity sections so pcolormesh/imshow plots drape correctly over terrain instead of assuming a flat z = 0 datum. It underlies terrain-aware section rendering used from Map Tools, Inversion, and AI inversion, and also exposes a one-call section function that accepts raw arrays, a pycsamt.interp.ResistivityModel, a pycsamt.inversion.results.InversionResult, native Occam2D or ModEM results, or AI inversion results directly.

Use this section when a section plot – pseudosection or inversion depth section – needs to reflect the real ground surface instead of a flat datum, or when you need fine control over how terrain is extracted, draped, and rendered. For the complete callable reference, see pycsamt.topo.

• 5.1. Terrain-Following Coordinates
  • 5.1.1. Reading the terrain from a survey
  • 5.1.2. The transform
  • 5.1.3. The PYCSAMT_TOPO singleton
• 5.2. Extracting Station Topography
  • 5.2.1. Any container, one answer
  • 5.2.2. Knowing when there is nothing to drape
• 5.3. Draping Flat Grids Over Terrain
  • 5.3.1. Interpolating between stations
  • 5.3.2. From station positions to mesh nodes
  • 5.3.3. Masking cells that end up above the surface
  • 5.3.4. Vertical exaggeration, and where it does not reach
• 5.4. Terrain Overlays on Section Axes
  • 5.4.1. Set the axes limits first
  • 5.4.2. Station markers and label thinning
  • 5.4.3. The pseudosection strip: station index, not real distance
  • 5.4.4. A plain label helper
• 5.5. One-Call Topography-Embedded Sections
  • 5.5.1. Any model, one grid
  • 5.5.2. Resolving topography
  • 5.5.3. Depth window and units – a real gotcha
  • 5.5.4. Colour scaling ignores outliers by default
  • 5.5.5. Default styling: white air, white markers
  • 5.5.6. Terrain-draped section, one call