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最大の視野を持つ観測点の決定

ToryElmore

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私は25,000エーカーの保護区にラジオリピーターを設置する最適な場所を探しています。したがって、ハイキングトレイルまたは道路から1/4マイルのバッファ内にある、保護区の最大の視野を持つ地点を特定する必要があります。保護区の境界、DEM、トレイル／道路、および1/4マイルのバッファのレイヤーはすべて配置済みですが、次にどう進めればよいか分かりません。viewshedとobserver pointツールがあることは知っていますが、それらをどのように使って目的を達成すればよいか確信が持てません。 <\/P><\/BODY><\/HTML>

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Conservation

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DanPatterson_Retired

are there any fire observation towers in the preserve?

ToryElmore

There are not, unfortunately.

DanPatterson_Retired

I was just trying to think of a shortcut for you to potentially find sites with optimal view. You could isolate areas of maximal elevation within your polygon buffer, however, that still doesn't guarantee that would be the optimal site. In any event, I doubt that a ground based point is going to be appropriate so perhaps you have other options (like a tower) that you are considering. This could broaden the candidate sites since there is going to be more that elevation that needs to be considered.

DarrenWiens2

I would start by identifying ridgelines and sampling those pixels as potential observation points. You can get at ridgelines by finding pixels where flow accumulation = 0.

ChrisDonohue__GISP

I'd start with the suggestion by Darren Wiens, and then consider using Modelbuilder (or Python) to iterate a Viewshed on each potential point (this may take several hours of run time), then compare the results.

Some thoughts/questions:

If you have not done a Viewshed before, I would do some trial runs to get a feel for it.
If you can employ a tower, you will need to know the height for the OFFSETA (attribute field)
It will probably be worthwhile to employ a RADIUS2 value (attribute field) to exclude distant cells outside your area of interest (this will help reduce processing time). For the same reason, it may be useful to employ a AZIMUTH1 and AZIMUTH2 (attribute fields) if your observation point is to one side of your buffered area.
The Curvature and Refraction corrections could get interesting, as they are designed for light. How does your radio signal propagate? Is it line-of-sight or does it go further?
Does the Repeater receive signals from another radio source? Would it be limited in placement by where it could receive the signals to repeat?
For best results a complete DEM will be needed. I mention this as your example seems to be missing some portions of the DEM where there is a trail buffer.

ArcGIS Help (10.2, 10.2.1, and 10.2.2)

Chris Donohue, GISP

ToryElmore

Ok, these all seem like good suggestions. I need to try out the Viewshed tool a bit before I determine how to proceed. The DEM is clipped to our property boundaries, but I see now that the inholdings need to be represented regardless.

ChrisDonohue__GISP

Another idea:

Besides Viewshed, look into Visibility (Spatial Analyst). I have not used this tool, but it seems to have much of the functionality of Viewshed but with some added functions. Using an analysis type set to Frequency may be the way to go.

ArcGIS Help (10.2, 10.2.1, and 10.2.2)

Chris Donohue, GISP

DanPatterson_Retired

Iteractive visibility add-in http://www.arcgis.com/home/item.html?id=c6d74b84ab37454d9ae8cae6bbe4955f

Viewshed along a path (just add tower height to the extracted path elevation:

http://www.arcgis.com/home/item.html?id=3528bd72847c439f88190a137a1d0e67

ToryElmore

I decided to use Flow Direction & Accumulation to ID ridgelines. I converted those pixels to a point shapefile, then split the shapefile into individual points using Dan Patterson's Split Layer By Attributes tool. I used Model Builder to iterate Viewshed on each point. Need some time to let it process, but I am hopeful.

If you have suggestions on what I should do differently, I'd still like to hear them. Thank you Dan Patterson, Darren Wiens, and Chris Donohue, GISP

DanPatterson_Retired

please post your results...I would be interested in seeing the product.

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