deminterpolationland-surveyqgistopography
Is there a way to create a relatively precise topographical map of a private land using GPS elevation data? As the land is a little bit over 100,000 square meters, the available regional topographical maps in Canada lack the precision I'd like to have for this project.
I have abundantly walked the land with a GPS and hence have thousands of points with elevation. Is there any way I could turn this into a somewhat interesting DEM or contour lines with QGIS?
there are lots of information about creating dem. but you must be clear about what data you have?
i hope it helps you...
Have you tried lowering the resolution of your raster data before creating the plot? Unfortunately, R is still slow for plotting large images so there is a trade-off between resolution and plotting speed.
# reduce raster resolution
dem_lower_res <- aggregate(dem, fact=10)
then plot
dem.p <- rasterToPoints(dem_lower_res )
df <- data.frame(dem.p)
colnames(df) = c("lon", "lat", "alt")
p1 <- ggplot(df, aes(lon,lat)) +
geom_raster(aes(fill = alt))
Best Answer
In QGIS you can use the Interpolation plugin (I think it is installed by default, if not it is a standard plugin installed through Plugin Manager) found in Raster -> Interpolation.
With that plugin you can take your vector layer of points and turn them into either a TIN or a surface model. You can either pull the elevation from a field in an attribute table or from the Z-Value if the points are true 3d points.
For a surface model select Inverse Distance Weighting and give the output file a .tif extension and you'll have a tif surface model that can be used to build contour lines, drainage models, etc.
The accuracy of the resulting data will depend on the accuracy of your GPS device, the number of points collected, and if they were collected accurately.