1

I've created a raster mosaic from OS 5 contour data to then process a number of viewsheds.

The issue is the area im working with is an island surrounded by sea so my mosaic is has no data in the areas of sea leaving holes when I make the viewsheds.

Is there a way to add blank/dummy rasters for these areas?

Raster mosaic with gaps in

1
  • 1
    Welcome to GIS SE. What have you tried so far? and have you looked into applying a raster mask? Feb 17, 2017 at 11:56

1 Answer 1

1

An ASC raster file can be viewed and edited in a text editor. An OS Terrain 5 tile will have a height measurement at every 5m so will be made up of a grid of 1000 columns and 1000 rows. If you were to apply zero at each record in this grid you would create a flat 5km 'sea tile'. The only other edit required is to change the x,y values, these are set to the bottom left corner of your tile in order to georeference the grid.

The first 6 rows of an .asc file are supplied below as an example:

ncols 1000
nrows 1000
xllcorner 100000
yllcorner 600000
cellsize 5
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 ..... 

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.