Sep 17, 2018. Geodesico sean convertidos a Coordenadas Planas (Topograficas o. To Planar Coordinates (Topographic or Local), in such a way that the. 0 H A M E / L O C A L. ' n u m b e fi. C O O IID ItliT f: l.& i'A V l i r W U O E L. M i G i.E: NVfL 8E. C u l t o r i in o r it i. TABLAS PARA TRANSFORMAR COORDENADAS UTM A GEODESICAS. G. 30 7. 00.
Follow Along: Guardando un Conjunto de Datos en Otro SRCRemember when you calculated areas for the buildings in theClassification lesson? You did it so that you could classify thebuildings according to area. Open your usual map again (containing the Swellendam data). Open the attribute table for the buildings layer. Scroll to the right until you see the AREA field.Notice how the areas are all very small; probably zero. This is becausethese areas are given in degrees - the data isn’t in a Projected CoordinateSystem. In order to calculate the area for the farms in square meters, the datahas to be in square meters as well.
So, we’ll need to reproject it.But it won’t help to just use ‘on the fly’ reprojection. ‘On the fly’ does whatit says - it doesn’t change the data, it just reprojects the layers as theyappear on the map. To truly reproject the data itself, you need to export it toa new file using a new projection.
Right-click on the buildings layer in the Layers list. Select Save As.
In the menu that appears. You will be shown theSave vector layer as. Dialog. Click on the Browse button next to the Save as field. Navigate to exercisedata/ and specify the name of the new layer asbuildingsreprojected.shp. Leave the Encoding unchanged.
Change the value of the Layer CRS dropdown to SelectedCRS. Click the Browse button beneath the dropdown. The CRS Selector dialog will now appear. In its Filter field, search for 34S. Choose WGS 84 / UTM zone 34S from the list. Leave the Symbology export unchanged.The Save vector layer as.
Dialog now looks like this:. Click OK.
Start a new map and load the reprojected layer you just created.Refer back to the lesson on Classification to remember how youcalculated areas. Update (or add) the AREA field by running the same expression as before:This will add an AREA field with the size of each buildingin square meters.
To calculate the area in another unit of measurement, for example hectares,use the AREA field to create a second column:Look at the new values in your attribute table. This is much more useful, aspeople actually quote building size in meters, not in degrees. This is why it’sa good idea to reproject your data, if necessary, before calculating areas,distances, and other values that are dependent on the spatial properties of thelayer.