Lecture 8: Topgraphical modelling
What does terrain influence?
building, transportation and drainage costs
What does topography indirectly influence?
soil erosion
Topography can be presented in which type of data:
Raster and vector data
TIN =
Traingular Irregular Network
What are the three continuous data in digital form?
DEM, DTM, DSM
How is topographical in raster form created?
created by interpolation
Cell value in topographical raster data represents:
the elevation in the centre of corresponding surface
What are the difficulties with DEMs
Sinks and flat areas
Why are sinks and flat areas a problem?
problem in hydrological modelling
How to solve sinks and flat areas?
Either fill the sinks and create a slope or use program that can handle the situation
When to estimtate volumes?
if we want to build a road and estimate cutting and filling volumes
How to estimate volumes?
check differences in elevation between the cells and the planned road by multiply by cell size
DTM is derived from a...
DEM
What is drainage direction?
the flow direction of non blocked surface water and equals the aspect values
What is viewshed
the field of view
The results of all DEM/DTM operations are VERY sensitive to...
cell size
The zenith angle to the object of interest has to be..
the smallest of them all if the object is in view