Carrying out a cadastral survey with a total station, apart from having millimeter precision, can also be useful for other purposes, since we have the elevation of each point. Let's see in this case, how to generate contour lines, which we already saw with AutoDesk Civil 3D, with Bentley Geopak y Manifold GIS, so for educational purposes, in this case we will do it with ArcGIS.
1. CAD data
For this exercise, I have the survey files in dgn, one for each work day. Importing it is as simple as:
- Data interoperability
- Quick import
The dgn files are selected, and voila, in all of them. See how beautiful they look themed, you can see the days the boys worked, when they made an effort and when They cheered.
More than interesting, you can see where they took points, in this case almost only in the direction changes of the blocks, to take the fronts and bottoms with a measuring tape. Practical to support the survey method for the time of mismatch with documentary measurements or other surveys. You can also see where they mounted the equipment to look back.
2. Enter points to the geodatabase
For better handling, I will input the points to a geodatabase. To do this, we assume that it is already created with the ArcCatalog and defined a Feature class.
- Conversion tools
- To geodatabase
- Feature class to geodatabase
3. Create digital model
Several of these steps can be overlooked, but for the purposes of understanding the use of 3D Analyst, we will see them in this order.
- 3D Analyst tools
- Create terrain
With this we have only defined the name of the model, we will enter the points:
- Add feature class to terrain
- Build terrain
Now we are going to generate the TIN
- ArcTool box
- 3D Analyst tools
- TIN creation
- Create TIN
You can see that at the ends that there are not enough points the triangulation stays poor, but where the streets are, consistency remains.
I could also notice that due to their innocence, in this lift the boys erred by not conserving the lift in a change of the apparatus. Savable error, by interpolation of nearby points but the observation can be had in time to make the corrective. Also suggest that in the first two georeference points they use the elevation coordinate provided by the GPS and sufficient distance to reduce the rotation error due to the inaccuracy of the GPS.
4. Generate contour lines
Always within 3D Analyst
- TIN Surface
- TIN Contour
Here we choose the newly created TIN, the target layer and interval between the contours (among others pirouettes Which saves me for space reasons).
The steps are more when compared to Manifold GIS, but the options are much more powerful.
5. Generate slope map.
- TIN surface
- TIN Slope
What is coming is to use this, which can be applied to the design of sewage systems, as this is not only a land survey, but a topographic survey with which you can work street profiles with just a couple of steps .