Creating Contour Map Using SRTM and QGIS

by : Bayu Yanuargi

Contour map is a map that contain the lines which are connected the location with a same elevation. Ussually the elevation are based on sea level but not must, some work not using sea level as a benchmark they prefered to use local benchmark point to get more detils calculation. On this posting we will talking about how to create a contour map using SRTM data that provided by free and for the GIS software, we will using QGIS that's free as well.

Ok, first we will talking about SRTM data. SRTM is Shuttle Radar Topography Mission part of NASA mission for topography mapping in whole world using sattelite imagery processing. The resolution of the sattelite Imagery is quite small with contour interval only 90 meters. 

Next step is we need to download the SRTM data for the area we want to mapped. You have to download the data directely from this link http://srtm.csi.cgiar.org/SELECTION/inputCoord.asp

When you click above link, you will redirect to SRTM downloader website. On the map you will see the grid, click on the grid for the area you want to download.

After we have choose the area of interest, then press the "Click Here to Begin Search" to start the data searching. After that the new page with the result list will be displayed, choose the "http downloaded" to download the data. The data format is on winzip, extract the data to the certain folder.

We have got the SRTM data in the raster format, now will use QGIS to process the data to be contour data in shapefile format. If you haven't QGIS yet you can download it by free to this link https://www.qgis.org/id/site/forusers/download.html , then install the downloaded QGIS software to your computer and open it after the installation is complete.

On the Browse Panel double click on your SRTM data (TIF) to displayed it to your display map like below picture.

Now we will do the processing to produce the contour map using our SRTM data. To do this process we nee to use GdalTool. This tool located on the Raste Menu, if you can't found it you need to install the tool. To install it go to PLUGIN --> Manage and Install Plugin. To activate it go to Installed Tabs and mark the GDALTOOL Box, if it is not there, you can go to Not Installed tabs and find the GdalTools there and install it.
 

To starting the contour creation, go to Raster menu --> Extraction --> Contour.

On the above picture you have to decide the output location and the contour interval you want to produces, on this excercise i use 10 meters for the contour interval. The result will be like on below picture.

Thats all how we create the contour map using SRTM and QGIS, if you have question please do not hesitate to leave comment below. Good Luck !!