This Tutorial shows Routing Calculations. You learn about
opening a Cartographic Data Set (openCartoDB) containing Height Data
opening a GPX Data Set containing 2D Data
generating Height Contour Levels from the Height Grid
MensorGIS has a proprietary XML Data Format for storing Cartographic Features (Menues „Import-openCartoDB“/„Export-openCartoDB“):
openCartoDB (open Cartographic DataBase) XML Format;
it defines and creates 10 Object Classes during the Import Process;
it has a distinct Graphic Layout (Colors/Sizes/PointSymbols/LineTypes/AreaHatches).
for more Information see OpenCartoDBTutorial.htm.
Tracking Information of GPS Handhelds is also often of interest (Menues „Import-GPX Data“/„Export-GPX Data“):
Point Features are created (WayPoints);
Line Features are created (Tracks);
also restricted Export is possible.
A typical Cartographic Functionality is Generation of Height Contour Levels (Menu „Height Data“):
the Information of a certain Object Class can be selected (Coordinates and one Attribute containing the Heights);
different Interpolation Methods are available (NearestNeighbourhood/InverseDistance/InverseSquaredDistance);
after processing the Contour Levels the Number of Steps and the Contrast can be adapted (Threesholding/Scaling).
Menu „File - Import - openCartoDB“
select „openCartoDGMerg.xml“
answer the Question on Identity Check with „No“
-> 8 Object Classes get created, 1 is them are used (Points): grid(lines) with 630 Points
Menu „File - Import - GPX“
select „Ergoldsbach.gpx“
answer the Question on Identity Check with „No“
-> 1 Object Class gets created (Lines): Streets of OpenStreetMap
Menu „Height Contour Levels - Compute Contour Levels“ -> Window „Height Contour Levels“:
select Object Class „OCDB_DTMgrid“
select Attribute „heights“
select Interpolation Method „Inverse Distance (4)“
let the ComboBoxes for Threeshold (32) and Contrast (0.50)
press Button „Calculate“
the Percent Number/Progress Bar show the State of computation (if you want to stop the computation then press „STOP“)
when computation is finished the Height Contour Levels get displayed
change the Number of Steps for the Threesholds and press the „Redraw“ Button
change the Scaling for the Contrast and press the „Redraw“ Button
toggling the Button „Height Plot OFF/ON“ changes the Display State
close the Window (OK)
Remarks on Interpolation Models:
There are different kinds of Interpolation Models: Weighted/Unweighted, Geometrical/Statistical, etc.
Usually an Interpolation is done by a Triangulation of the Height Points and in the resulting Triangles a certain Interpolation Model is used.
Geometrical Models are e.g. (Bi)Linear Interpolation, (Bi)Quadratic Interpolation; Statistical Models is e.g. Collocation.
The problem of using Triangulation is that only inside the Tringulation Network an Interpolation can be done; outside it would be an Extrapolation.
Geometrical Models can become inaccurate in Extrapolation Areas; Statistical Models are more stable.
MensorGIS implements different kinds of Statistical Models to be able to always get a Rectangluar Area around the Height Points.
These Models are of different quality: Nearest Neighbourhood is the simplest and not to accurate; the Inverse Distance Models are more exact.
Threesholding the Steps and Scaling the Contrast are Terms used in Digital Image Processing; here they are used to adapt the result to your needs.
The Height Contour Level Raster can also be exported using Menu „File - Export - SVG“.
MensorGIS Version 1.1.1, 2012/03/29