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It is not always easy positioning existing sites on a 3D Digital Terrain Model (DTM). For example, Wireless local loop (WLL) operators, who use 3D maps with a resolution of between 1 and 4 meters, are faced with the inadequate precision of the site coordinates that they are given. How do you subsequently go about placing a base station as best you can on the right building using ICS Telecom when you don’t always know the building by sight? How do you find the highest point identified by the negotiating engineers in the field on the map?

As we all know, coordinates do not give an absolute position, but one with a margin of error that varies according to the techniques used. A positioning error of around 25 meters is obtained when measuring a position on a geo-referenced 1/25000 scale map. The precision of the coordinates currently obtained using one of the better GPS systems is around 10 meters (remember it used to be around 100 meters when the signal was still encrypted by the US Department of Defense). In addition, some sites are officially identified by their coordinates. These may be incorrect by tens or even hundreds of meters, but they cannot be changed. Finally, some lists of coordinates were drawn up at a time when a precision of around 4 meters was unnecessary and they have not always been updated since.
Now operators seeking to use ICS Telecom to place and validate the sites they own or rent cannot accept such positioning errors. The site’s position must be accurate to within a few pixels (with 1 to 4 meters per pixel depending on the resolution of the electronic measurement data used).
Coordinates are therefore insufficient. Additional information on the site is needed, such as the elevation of the ground and the building or even of the terrace to be used, or a map excerpt with the precise plotting of the station (ideally a cross drawn with a ruler on a map where the buildings are shown). Photographs of the building or panoramic views taken from the roof are not necessary.

Operating mode using ICS Telecom:
The project’s mapping must first be converted into the code for projecting the coordinates of the sites to be placed (refer to cartographic conversion in the tools menu or in the reference manual: cartographic conversion: projection systems).
A site can be positioned on the map using the coordinates provided by complying with the following procedure:

- Press the «p» key on the keyboard.
- Enter the coordinates of the station in the related projection. If necessary, change the current projection using the Coordinate conversion button.
- Click on Preview to ensure that the coordinates are consistent with the current project.
- Click on Update to place the site: the station’s parameter box appears.

The station must now be repositioned. If the operator does not have any other information on the site, it can then look for the highest point within a radius of a few meters (assuming that the site is located at the highest point in the area):

- Left click on the station and choose Move.
- Right click on the station and choose Highest point...
- Enter the maximum search distance and click on OK.
- Then double-left click or press Enter twice on your keyboard.

The image of the area (road map, satellite photograph, etc.) can also be used with ICS Telecom to identify the possible presence of a water tower, a mast, or any other noticeable site.

The operator can identify the site more easily if it has, in addition to the coordinates, the plotting map and the elevations of the building and the ground. The building on which the station is to be placed can be identified on the ICS Telecom image by comparing it with the plotting map. This is because the plotting map is drawn up in the field and leaves little ambiguity concerning the exact location of a station. The building’s height can serve to distinguish between a number of buildings or terraces on the same block. The height can be measured using ICS Telecom by subtracting the roof elevation from the ground elevation at the foot of the building and comparing it with the data provided.
After moving the station to the appropriate site, you need to use the 3D map (DTM) to check that the station is indeed on a high point, as there may be slight discrepancies between the image and this map.

Digital terrain models with sufficient resolution can also be used to position the station and the sectors on the edge of roofs. This operation can be done automatically on one or more stations. For this purpose, draw a frame around the stations to break out using the Select rectangle, tool and then choose Break out stations... Then define the maximum distance, how to move it and the clutter code onto which each sector is to be moved.