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Creating a Single Contour

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#1
BTN123

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Hi All,

I am looking to simulate sea level rise on a coastal location. I have LiDAR data and aerial imagery of the area which I have already input into ArcMAP. I want to create a single contour to represent a sea level rise of a certain amount (i.e. +1m). Does anyone have any idea on how I would go about doing this?

Any help is much appreciated!

#2
Crischan

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If you have the Spatial Analyst extension available for ArcGIS, use the Contour List tool from the surface toolbox and enter the altitude you need to simulate an 1m rise.
Crischan Wygoda
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#3
aug_aug

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Another easy way to do this is to create a contour layer from the lidar dem, with the Spatial Analyst/3D Analyst extension, then just symbolize (symbology by category - "1m, 2m, 3m, etc.") the lines based on the contour values, group all of the contour lines that you don't want to show up and change their color to "no color", symbolize the one you want to display however you like.

You'll be left with only the contour line you want and it's easier to change if your elevation changes or you want to display additional contours (just ungroup - regroup).

#4
BTN123

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Another easy way to do this is to create a contour layer from the lidar dem, with the Spatial Analyst/3D Analyst extension, then just symbolize (symbology by category - "1m, 2m, 3m, etc.") the lines based on the contour values, group all of the contour lines that you don't want to show up and change their color to "no color", symbolize the one you want to display however you like.

You'll be left with only the contour line you want and it's easier to change if your elevation changes or you want to display additional contours (just ungroup - regroup).


Thanks for the advice, this is exactly what I was looking for! Is it possible to get a bit more detail on how to perform the analysis (creating a counotur layer from the lidar DEM) as described above?

Much Appreciated!!!

#5
aug_aug

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Well, to give you more detail, I'll need to know what form is your lidar data in exactly, and do you have available the Spatial Analyst or 3D Analyst extensions?

You can check by clicking at the top - Tools>>Extensions...>>then you'll see a list of available extensions.

#6
BTN123

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Well, to give you more detail, I'll need to know what form is your lidar data in exactly, and do you have available the Spatial Analyst or 3D Analyst extensions?

You can check by clicking at the top - Tools>>Extensions...>>then you'll see a list of available extensions.


OK. The LiDAR came in ASCII grid files, whcih I have stretched and converted to raster as a 32-bit float file. I have both the Spatial Analyst and 3D Analyst extensions. Thanks for your help!

Much Appreciated!

#7
aug_aug

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So just use the 3D Analyst > Surface Analysis > Contour, select your contour interval (+/- 1m in your first post indicates you'll need a 1m interval to select individual contours), then under the Symbology property choose Categories > Unique Values > then Add All Values for the "Contour" Value Field (drop down). At this point you'll see all of the individual lines which you can shift- cntrl-click like you would a list of files and symbolize how you like.

#8
BTN123

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So just use the 3D Analyst > Surface Analysis > Contour, select your contour interval (+/- 1m in your first post indicates you'll need a 1m interval to select individual contours), then under the Symbology property choose Categories > Unique Values > then Add All Values for the "Contour" Value Field (drop down). At this point you'll see all of the individual lines which you can shift- cntrl-click like you would a list of files and symbolize how you like.


Thanks, I was playing around with the data yesturday and managed to do what you have listed above! So I now have a single contour for the level of inundation, is there any way I can fill the areas (elevations) below this contour with a colour to more effectively simulate a flood???

Much appreciated!

#9
aug_aug

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The first (easiest) thing that pops into my head would be to select the line you want, right-click on the Layers tab, convert features to graphics (don't delete feature). So now you have a graphic line, I'm not sure at this point, but I think you can now use the Drawing tools to add vertexes (sp?) to the line and "draw" your polygon.

You could then convert the "graphics to features" just as you did initially after you've made your polygon. By doing this you could adjust the transparency of the layer, making it see-through and more flood-like, or calculate the flooded area, create a buffer, etc. - all the things you can do with features.

Hope that helps, if you'd like to chat you can IM me on Yahoo, or MSN anytime (Well, a convenient Pacific time).

#10
BTN123

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The first (easiest) thing that pops into my head would be to select the line you want, right-click on the Layers tab, convert features to graphics (don't delete feature). So now you have a graphic line, I'm not sure at this point, but I think you can now use the Drawing tools to add vertexes (sp?) to the line and "draw" your polygon.

You could then convert the "graphics to features" just as you did initially after you've made your polygon. By doing this you could adjust the transparency of the layer, making it see-through and more flood-like, or calculate the flooded area, create a buffer, etc. - all the things you can do with features.

Hope that helps, if you'd like to chat you can IM me on Yahoo, or MSN anytime (Well, a convenient Pacific time).


Thanks, you've been a great help, I'll have a play around with what you have suggested above and will let you know how I get on!

Much Appreciated!

#11
BTN123

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The first (easiest) thing that pops into my head would be to select the line you want, right-click on the Layers tab, convert features to graphics (don't delete feature). So now you have a graphic line, I'm not sure at this point, but I think you can now use the Drawing tools to add vertexes (sp?) to the line and "draw" your polygon.

You could then convert the "graphics to features" just as you did initially after you've made your polygon. By doing this you could adjust the transparency of the layer, making it see-through and more flood-like, or calculate the flooded area, create a buffer, etc. - all the things you can do with features.

Hope that helps, if you'd like to chat you can IM me on Yahoo, or MSN anytime (Well, a convenient Pacific time).


Hi again!

I've tried playing around with what is suggested above, I managed to get to the add vertices stage but couldn't seem to make any progress from here! Any further advice on how to do this, or other suggestions as to how I may go about colouring the areas/elevations below the flood contour???

Much Appreciated!

#12
Nicholas_C

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Although the above mentioned process would work fine, Here's another fairly easy method you could use.

In ArcCatalog create a new polygon shapefile to represent your "flood".

Add the shapefile to ArcMap.

Start editing and choose the flood layer.

Select "create new feature" then use the trace tool.

Trace the selected contour in your area of interest, then click once but don't double click and go choose the drawing/pencil tool.

Draw out to whatever extent you need off the coast for the purposes/extent of the map.

Save your edits, then add whatever fields/attribute information you desire, then save edits again and stop editing.

If you need to add new areas you could always draw then in using the method above and dissolve them together to create a single feature.



Keep in mind that this is just a 2d polygon shape but for graphical display purposes should work fine. There are some more complicated ways to achieve this in spatial analyst - some cut/fill operations - but it sounds like for the purposes of a 2d map a simple polygon will suit your needs.

Hope that is helpful, and understandable.

#13
aug_aug

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Well to add vertices while editing just hover over the line and right click, you'll see "add vertex" a ne wpoint should appear, which you can then drag to wherever you want...

http://webhelp.esri....leting_vertices




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