Skip to main content
Question

How to add 2 metre elevation offset to Mean High Water Spring


gisgeek
Contributor
Forum|alt.badge.img+9

I have a MHWS and along the MHWS line the elevation from the DEM varies. I want to locate the 2metre elevation point relative to the MHWS Line. Could you please suggest an approach that would work to identify this and convert to a lineimage

5 replies

hkingsbury
Celebrity
Forum|alt.badge.img+53
  • Celebrity
  • January 19, 2023

Thats a really interesting problem. My initial thought would be:

  1. Add points every X meters along the MHWS (depends what resolution you want), make sure they're numbered in order
  2. Overlay these points on the DEM, you now know, for points every Xm what elevation it is on the DEM
  3. Then, using an AnchoredSnapper (segment snapping) snap those points to the +2 elevation
  4. Rebuild the line

 

One thing to be cautious of is how will this behave with (from the inland side) with very concave angles

image


gisgeek
Contributor
Forum|alt.badge.img+9
  • Author
  • Contributor
  • January 25, 2023
hkingsbury wrote:

Thats a really interesting problem. My initial thought would be:

  1. Add points every X meters along the MHWS (depends what resolution you want), make sure they're numbered in order
  2. Overlay these points on the DEM, you now know, for points every Xm what elevation it is on the DEM
  3. Then, using an AnchoredSnapper (segment snapping) snap those points to the +2 elevation
  4. Rebuild the line

 

One thing to be cautious of is how will this behave with (from the inland side) with very concave angles

image

Should this work with just points and raster? I have converted line to points and extracted value from DEM to point for those point. When I try anchored snapper against the DEM it doesn't give me any values.


gisgeek
Contributor
Forum|alt.badge.img+9
  • Author
  • Contributor
  • January 25, 2023
gisgeek wrote:

Should this work with just points and raster? I have converted line to points and extracted value from DEM to point for those point. When I try anchored snapper against the DEM it doesn't give me any values.

image


hkingsbury
Celebrity
Forum|alt.badge.img+53
  • Celebrity
  • January 25, 2023
gisgeek wrote:

Should this work with just points and raster? I have converted line to points and extracted value from DEM to point for those point. When I try anchored snapper against the DEM it doesn't give me any values.

I realise now I didnt add in one rather important step; convert the DEM to contours and use that to snap the points to - sorry!


gisgeek
Contributor
Forum|alt.badge.img+9
  • Author
  • Contributor
  • January 25, 2023
gisgeek wrote:

Should this work with just points and raster? I have converted line to points and extracted value from DEM to point for those point. When I try anchored snapper against the DEM it doesn't give me any values.

Ok that makes sense. Thanks for your help


Cookie policy

We use cookies to enhance and personalize your experience. If you accept you agree to our full cookie policy. Learn more about our cookies.

 
Cookie settings