Create Coastline from Outline of Raster Image

[AliciaVenkatachalam]

Hello,

I am trying to create a simple polyline to represent the coastline of Sri Lanka...but I want to match the one portrayed in a raster SRTM elevation image exactly. I have the file as an .asc and a .rrd/.aux file.

I am unsure how best to do this? I tried to convert the raster to both a polygon and a polyline but the file is too big even if I crop it first and my computer crashes trying to display it. I have tried using some of the functions in ArcScan but I am just not sure if this is the correct method or how to set it up if it is?


Many thanks for any advice anyone can offer!

[AliciaVenkatachalam]

Thank you so much.... I just created my coastline this morning!

[SanderFox]

Sorry to bump this thread up again, but I'm having a similar problem. I have created a raster with only two categories representing land and water, but I can't find how to turn the divide into a polyline. Any help is much appreciated!

Sander

[SanderFox]

It got it, finally. With the IsNull function I had made the division between land and sea. At first I couldn't find out what to do next (hence my previous post), but in the end I used the Zonal Fill function (input zone = my dem, input weight = IsNull output), filtering out the non-land part. Then I used Raster to Polygon and Polygon to Line to get the coastline. Maybe Raster to Polyline would have worked as well, but I didn't try it.