QGIS Lab03 Fall14: QGIS Openlayer Plugin, Geocoding, Bulk Geocoding, and Raster Analysis

Introduction:

This is third video tutorial in urdu language for QGIS. It is overview lecture on basic tasks such as openlayer, geocoding and raster analysis.

Summary:

  1. Openlayer (google map and open street maps)
  2. Geocoding and reverse geocoding, bulk geocoding using MMQGIS (block/bulk of addresses at same time)
  3. Raster Analysis
    1. Interpolation
    2. Heat Map
    3. Terrain Analysis
    4. Slope
    5. Hill Shade
    6. Projection Wrap Projection
    7. Extraction:
      1. Contour
    8. Clipper/subsetting (corp)
    9. Miscellaneous
      1. Merge/mosaic (combine)

Below is the full video lecture. Use full screen for clear content of video. The download link of below video is ogg video or mp4 video. You can play it in vlc player or open it in web browser.

The example files that are used in video can be downloaded from here .

Reference:

  1. Openlayer
  2. Geocoding
  3. Raster Based Terrain Analysis Techniques
  4. Clipper and Contour
  5. Mosaicing and Clipping

Contour Plot using Matlab

You can plot contour map in Matlab. All you need is following:

  1. Download the zipped file of contourmatlab that contains m files, xls file of sample data and world mat file. The file is distributed under GNU/GPL v2.0 license.
  2. Extract the zipped file of contourmatlab to required directory.
  3. Open matlab and set your current directory of matlab to the extracted folder.
  4. Change the data in data.xls file to your own data. Remember that first column is latitude, second is longitude, both in decimals. While third column is value which you want to plot in contour. Same Latitude and Longitude should not repeat in rows.  For good contour plot, given data should be well distributed.
  5. In matlab command line, type:  plotcont
  6. Your contour will be plotted.
  7. To change the region of your plot or spacing of the plot data, you must edit plotcont.m file.

    Figure of Contour Plot on Pakistan Map.
    Fig1. Contour Plot on Pakistan Map.

You can use this file to plot the elevation contour of given region. All you need is to take latitude, longitude and elevation data for the required region. You can use google earth for this or if only elevation data is required then use online elevation profile.

Contour Map from DEM file

Prerequisite Software: ArcGIS 9.3

  1. Download the required DEM file from DEM Datasources. One of the datasource for DEM files is databasin. For following example, I downloaded Asia DEM file.
  2. Extract Portion of DEM Geoprocessing in ArcMap.
    1. Open new empty map in ArcMap.
    2. Drag and drop your DEM file from ArcCatalog to ArcMap. In my case, the dem file is 000asia_dem.
    3. Open ArcToolbox from icon on Standard Toolbar in ArcMap or from Windows>ArcToolbox.
    4. In ArcToolbox, click Spatial Analysis Tool > Extraction > Extract by Rectangle. In my case, I have entered following coordinates:
      • left = 70.59
      • right = 73.064
      • top = 34.849
      • bottom = 32.525
    5. Select aisa_dem in inputraster dropdown box.
    6. Browse to your given folder in output raster box and press ok. Also enter the name of the file to save. In my case it is surveydata.
    7. Extracted DEM will be created as new layer.

  3. Create Contour from DEM file.
    1. Open new empty map in ArcMap.
    2. Drag and drop the extracted DEM file from ArcCatalog to ArcMap. If it ask to create pyramids for dem file, press yes.
    3. Open Spatial Analyst Toolbox from right click on empty space of Standard Toolbar or goto view > Toolbars>Spatial Analyst.
    4. Goto Spatial Analyst > Surface Analysis > Contour
    5. Select in input box the given DEM layer.
    6. Set the Contour Intervals or keep the default values.
    7. Select the Output folder for Feature and give name to the shape file. In my case the name is surveycontour.shp. Press ok.
    8. A contour file will be created as new layer.

You can check the dem2contour poster for demo.