![]() Hence, making maps in QGIS needs some explanation. ![]() I work with this project for over a year now and had no problems. QGIS uses the GDAL/OGR library to read and write GIS data formats. be/GlGBp4zj3vcCreate a 3D map in QGIS using a DEM, hillshade, and Google imagery. 12 (2 Solutions!!) Roel Van de Paar 120K subscribers Subscribe 0 24 views 1 year ago GIS: Google Maps not Showing in QGIS 2. To save data in Google Mercator: Right click on shapefile and select Save As Then I re-opened the original problem project, deleted all of the existing layers, saved it as temp with no data in it at all, and then closed and re-opened the project and re-loaded the problem shape layer into the new temp project. Take care that the option Save only selected features is activated.įigure 8 and 9 show the flooded areas in case of an event with a flood of 5m compared to the old ocean extent for the Accra region, Ghana.Qgis google maps not showing. The geometric predicate should be set to ‘intersect’ and a new selection should be created.Īfter the new selection has been created the polygons will be saved as a new water extent layer for the modelled flood height through a right-click on the polygonised layer (Export > Save Selected Features As), see Figure 7. The features of the polygonized layer from the previous step have to be chosen as Select features from and will be compared with features from a costal vector file. Therefore the polygonized potential water extent has to be intersected with a coastline vector to filter inland patches. To filter inland water patches, which fulfill the elevation threshold but are not connected with the ocean, the Select by Location tool (Vector > Research Tools > Select by Location) in QGIS is applied (see Figure 6). In addition the user can decide if the 8-way-connectivity should be considered for the conversion. After opening the tool through Raster > Conversion > Polygonize (Raster to Vector) the input and output files have to be defined. Besides setting the Input layer (Classification from previous step) and Converted output file, the NoData value has to be assigned to 0.Īfter defining the NoData value for the classification layer, the file is going to be converted to a vector file using the Polygonize tool. The tool is accessed via Raster > Conversion > Translate (Convert Format). An example is shown in Figure 3, where all pixels below or equal 5m are indicated in blue.įigure 3: Potentially flooded areas (flood level of 5m) indicated by blue for N05W001, Accra region, GhanaĪll dry areas in the classification mask are now set to NoData using the QGIS Translate tool. The result is a binary layer classifying all potential flooded areas by 1. Furthermore the Output layer as well as Output format has to be set. In this sample case a value of 5m has been set. Then set the threshold for the flood level you would like to simulate. Opening the Raster Calculator through Raster > Raster Calculator the window shown in Figure 2 will pop up.įirst, select your DEM layer and click on the ‘less or equal’ math operator to create a Raster Calculator Expression. ![]() In the next step, all elevation pixels below a certain elevation threshold will be detected. Figure 1 shows an example of the coastal region in Accra Region in Ghana, where the WorldDEMTM elevation data and the ocean extent of the WorldDEMTM Ocean Shoreline have been used.įigure 1: WorldDEMTM and WorldDEMTM Ocean Shoreline for N05W001, Accra region, Ghana ![]() First all data relevant for coastal flood modelling has to be loaded in QGIS: The Digital Elevation Model raster file and the Ocean extent vector file.
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