Sun & hill

topographic methods

@boyd.xyz/t

Yesterday in the Great Smokies
Webcam archive

UKy Geography Colloquium, 2025

Boyd Shearer

• Senior Lecturer, Department of Geography
• Online Digital Mapping program 🔗
• outrageGIS mapping trail maps 🔗
• Contact 🔗

Sun

D Rumsey Map Collection

• Eduard Imhof, 1895-1986 🔗
• Carte de France, 1750-1815 🔗
  • Tiled on a Google Map 🔗
• Hans Conrad Gyger, 1599-1674 🔗

😐

USGS Topographic maps

• 7.5 minute quadrangles are gold standard.
• 1880s–current 🔗
• USGS Topo View 💯 🔗
• Let's map forest trails.

First axiom: You must be present. Maps live in the areas they show.

A better day 🔗

Second axiom: Places are interconnected.

Hill

Lidar

• Lidar detection and ranging
• users lasers to sample the earth's surface
• and create a dense point cloud of elevations.
• KyFromAbove 🔗

Height model

• Lidar captures above ground features.
• DSM: Digital Surface Model.
• DEM: Digital Elevation Model.
• height = DSM - DEM

First use of height model visualizing floods

2022 floods

• Identify informal infrastructure prone to flooding.
• Notably, private bridges.
• Relative elevation model (REM) for height above river.

25 ft above Troublesome

• GEO509 report. 🔗

Measuring tree heights

A tree canopy model

• Use NAIP NDVI to identify trees.
• Extract heights from DSM.
• trees = (NDVI > x) & (height > y)
• National Agriculture Imagery Program (NAIP)
• Normalized Difference Vegetation Index (NDVI)

Caveats

• Temporal resolutions don't match.
• NAIP's profound vertical displacement.

Change: multitemporal analysis

Two statewide point clouds

• Simple math comparing DSMs.
• change = DSMP2 - DSMP1
• but trickier symbology.

Opportunities

• Fuse NDVI with DSM change
• to find loss and gain of tree canopy.
• loss = (NDVIP1 > x) & (heightP2-P1 < y)

Accurate?

• First axiom: get into the field.
• But, what about the historical observations?
• Google Maps Street View? 🔗 🔗

Third axiom: Places change.

(And if change
is incompatible with humans?)

🔗 VR: 🔗 🔗

Thank you