+3 m ± 2 m -1 m ± 2 m -7 m ± 2 m How do we account for error when differencing DEMs? We’ll consider four possibilities: 1. Just ignore it 2. Ignore it, but define some minimum level of detection (minLoD) 3. Treat it as spatially uniform, generate an error surface, and propagate it 4. Treat it as spatially variable, generate an error surface, and propagate it UNIFORM ERROR VARIABLE ERROR