1. Using ESRI ArcGIS 9.3 3D Analyst T I N
Advanced GIS
Using ESRI ArcGIS 9.3
3D Analyst
T I N

2. 3D Analyst
Activation
Be sure to have activated the 3D Analyst extension and load the toolbar.
Open the project “Base 3” located in the folder “Data 3”

3. 3D Analyst Elevation data
3D models are calculated basing upon appropriate source data.
Basically, contours and elevation point are used.

4. 3D Analyst Elevation data .
For more accurate models, more data can be used (e.g. rivers, roads, scarps etc.).
Almost all data can be extracted from topographic vector maps (Select by Attributes)

5. 3D Analyst
Mask
Always be sure to have base layers an area significantly larger than the analysis mask.
Otherwise, severe errors will occur along the borders

6. 3D Analyst
TIN
ArcGIS generates a TIN (Triangular Irregular Network) to interpolate elevation data and create a vector 3D model.
Connecting adjacent elevation points or nodes, triangles oriented in the 3D space are created, thus allowing to have a z for every possible x,y
Other GIS packages interpolate between vector data creating a raster map of elevation (one elevation for each pixel)

7. 3D Analyst
Create TIN
First of all, a TIN is to be created

8. 3D Analyst Create TIN For the first TIN, use only Elevation points
Check in the list of layers the proper one

9. 3D Analyst Create TIN Height Source
i.e. the location of the values to be used as local elevation.
It may be the Z value for 3D features or any numeric field

10. 3D Analyst Create TIN Height Source
i.e. the location of the values to be used as local elevation.
It may be the Z value for 3D features or any numeric field

11. 3D Analyst Create TIN Triangulate as
Method to be adopted for the interpolations.
Points can only be used as “mass points”

12. 3D Analyst Create TIN Triangulate as Lines allow three methods:
“mass points”
“hard line”
“soft line”
Generally, it is better to use the “soft line” method

13. 3D Analyst Create TIN source data Triangulate as
Lines allow three methods:
“mass points”
“hard line”
“soft line”
Generally, it is better to use the “soft line” method
source data
“mass points” 37 26
“hard line” 15
“soft line”

14. 3D Analyst Create TIN Triangulate as Polygons allow eleven methods:
“mass points”
“hard line”
“soft line”
“hard clip”
“soft clip”
“hard erase”
“soft erase”
“hard replace”
“soft replace”
“hard value fill”
“soft value fill”
3D Analyst

15. 3D Analyst Create TIN Triangulate as Polygons allow eleven methods:
“mass points”
“hard line”
“soft line”
“hard clip”
“soft clip”
“hard erase”
“soft erase”
“hard replace”
“soft replace”
“hard value fill”
“soft value fill”
same as for lines
Removes everything outside the polygon(s)
Calculates the TIN only inside the polygon(s)
Removes everything inside the polygon(s)
Calculates the TIN only outside the polygon(s)
Replaces the TIN with the values calculated only from the polygon(s)
As before, but allows the hidden objects to be taken into account
Similar to “replace”

16. 3D Analyst Create TIN Tag value field
An integer value can be stored in the TIN for every triangle and node.
They are typically used to store the accuracy of each elevation
3D Analyst

17. 3D Analyst Create TIN Result
Of course, the result obtained using only elevation points will be very rough.
Therefore, it is better to add at least the contours
3D Analyst

18. 3D Analyst Create TIN Adding Layers
To add a new layer to the calculation of a TIN it is possible either to create a new one using all the selected layers of to use the “Add Features to TIN” tool, upgrading the esisting TIN
3D Analyst

19. 3D Analyst Add Features to TIN
It is possible either to upgrade the source TIN or to create a new one
3D Analyst

20. 3D Analyst
TIN
The TIN derived from both elevation points and contour lines is much more detailed.
Anyhow, errors will affect the borders; therefore it is much better to include the mask to clip the TIN

21. 3D Analyst
TIN
The mask (polygon!) is to be used as soft clip (i.e. allowing to take into account also the features located outside the clip area).
Obviously, the “Height source” is to be set to “none”.

22. 3D Analyst
TIN
Result

23. 3D Analyst TIN Representation
It is generally better to remove the source features from the representation. If needed, is much better to activate the source layer(s).
To do this, deselect the “Edge types”

24. 3D Analyst
TIN
Representation
Result

25. 3D Analyst TIN Representation
Use a suitable color ramp (create it, if needed) and use a very small “Defined interval” (e.g. 1)

26. 3D Analyst
TIN
Result

27. TIN
Errors
The interpolation procedure almost always determines errors, such as flat tops and stepwise ridges and valleys
3D Analyst

28. 3D Analyst TIN Refinement
It is possible to ameliorate the result including further vector data sources, such as those representing the hydrography or the transportation network
3D Analyst

29. 3D Analyst TIN Refinement
Obviously, streams and roads have varying elevations, therefore they have to be stored as 3D lines (one elevation for each node) and the “X value” is to be used for the creation of the TIN

30. TIN
Refinement
Result
3D Analyst

31. 3D Analyst TIN Refinement Anyhow, some errors will remain.
When an error is due to a wrong value stored as elevation in a feature, obviously it has to be corrected editing the wrong figure.

32. 3D Analyst TIN Refinement
Other errors simply are the results of triangles created from three nodes having the same elevation.
To correct them, it is necessary to create new shapefiles (generally, one of points and one of 3D polylines) and use them to introduce new features in order to have a correct interpolation
3D Analyst

33. 3D Analyst TIN Refinement Correction Points
Smaller errors can be corrected adding a new elevation point.
The elevation can be desumed by the contours (faster if labeled).

34. 3D Analyst TIN Refinement Correction Lines
For larger errors, it is generally better to use 3D lines.
It is generally suggested to activate the snapping to both contours and elevation points

35. 3D Analyst TIN Refinement Correction Lines
Once drawn the line, it has to be edited to assign its proper elevation to each node.

36. 3D Analyst TIN Refinement Correction Result
This procedure is to be repeated until a good result is achieved.
Remember to close the editor before starting the creation of a new TIN
3D Analyst