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11

We usually have data concerning where the ground is, so we have to use that. The ground determines a solid figure in 3D. You project this figure radially onto the unit sphere centered at the viewer: this maps the ground onto a region in the sphere. Compute the area of the remaining region: that's the solid angle subtended by the sky (in steradians). ...


8

This is a known issue: http://support.esri.com/es/knowledgebase/techarticles/detail/17336 Basically it's a problem with using a raster layer in the inset maps. If you can only use vectors on your insets the transparency works.


7

Your choice of DSM vs DTM will depend on whether there is best-practice guidance or regulations governing the planning process for which you are performing the calculation. For instance, Viewshed Analysis for planning in the UK, especially for windfarms, requires that you use DTM data (and specifically Ordnance Survey data). Analysis with DSM may be used ...


6

Here's an answer that comes from the computer graphics world rather than GIS -- hence, it's a description of an algorithm rather than instructions for which tool(s) to use. Definition: a ray is an origin + a direction; it is the line that begins at the origin and continues to infinity along that direction. You need the following basic ingredients: ...


4

For a ZTV you would not normally use the Observer Points tool unless you need to know which turbine is visible at a given location and you have less than 16 turbines. Use the Viewshed tool. The simple setup you need for the calculation is like this: OFFSETA = turbine tip height (or hub height if requested by client) OFFSETB = 1.65 (in your case, I often ...


3

Ecotect (now an AutoDesk tool) enables you to do this. More generally, this is frequently examined in the area of daylighting and a tool from this field might be easier to use, than GIS. (Though I have heard of a GIS plugin that can do this and calculate solar exposure, but I've never managed to find it).


2

The sky-view factor (SVF) is defined by the part of the visible sky (Ω) above a certain observation point as seen from a two-dimensional representation (see figure a). The algorithm computes the vertical elevation angle of the horizon γi in n (eight are presented here) directions to the specified radius R (b). Sky-view factor has been proposed to overcome ...


2

You can do this with SQL. Without knowing how you're getting your data, I'd guess something like: SELECT ST_Intersects([the polygon geom], ST_LineFromWKB([point A geom], [point B geom])) AS Is_Obscured Obviously this is not a complete query. If it's not enough to point you in the right direction, then you'll need to share some more details.


2

Visit maxScale or minScale dont working in vector (from wfs) layer for a similiar question. maxScale:50000, minScale:25000 should be changed to: maxScale: 1/25000, minScale: 1/50000


2

You need to call setVisibility(true/false) on the layer. setVisibility All you are doing in your code is changing the value of static variables. This will not trigger any action on the layer. In your checkbox handler, you need to get a reference to the layer and change the visibility: triangleLayer1.setVisible(value);


2

You might consider using the Visibility Index, which is a measure of the size of the viewshed for each pixel in a DEM. This way you could measure the overall visibility of a pathway or route. I wrote a blog on the calculation of the visibility index and some of the challenges involved that you might find useful here: http://whiteboxgeospatial.wordpress.com/...


2

Have you considered using a model to automate this? You could use an iterator to step through each point and generate a view shed for it. Then if required merge the grids. If you do not know what I am talking about its time for you to open up desktop help and start reading up on model builder. This will allow you to automate this task.


2

You could use the iface.mapCanvas().layers() method, which gives you only the checked layers in the ToC, i.e., no need to iterate through all map layers. You should then iterate through checked layers to evaluate if their scale-based visibility contains the current map scale, like this: canvas = iface.mapCanvas() for layer in canvas.layers(): if layer....


2

The best way is to use viewshed (observer point does not seem necessary based on you question, except if you want to know which spire can see which WTG). First you determine the locations where you could see your WTG (viewshed of the spires), then you use "extract multivalue to point" to transfer this information from the resulting raster to each WTG point. ...


2

The most visible point... From where? From everywhere? How big is the area? What I suggest is creating a grid of regularly spaced points and using each one of those as observer points. I usually use Geospatial Modelling Environment to create regular points within a polygon. It's free to download and open source. Here's the command to do so. Run a ...


2

The Viewshed tool uses a single DEM as input. @MappaGnosis explains clearly that you must decide whether a DSM, DTM or a combination of the two is best for your input DEM. By default, the observers eyes are at DEM + 1 (default OFFSET A = 1). So, yes, if you use the DSM as your input DEM and specify nothing else the observers eyes will be one meter above the ...


2

I have a version 10.2.1 and tested exporting a dataframe (inset of Ontario) superimposed over a main dataframe and found that there are no issues any of the above-mentioned file types; PDF, EPS, JPG, TIFF (Example bellow) If I remember correctly some graphic-related transparency issues were addressed in the 10.2.1 version. If you do not have access to ...


1

One way to do this would be to add an attribute to your polygon layer, say "VALUE", and assign it numeric value of 1000 or more. Then convert the polygon layer to a raster. In arcpy using the spatial analyst module these rasters can be multiplied easily. elevRast = arcpy.Raster("path/elevrast") polyRast = arcpy.Raster("path/polygonraster") resultRast = ...


1

If there is another layer on top of the new one you have created, then you can alter the order of the layers in the 'List by drawing order' table of contents.


1

Using a DSM is pretty much required for viewshed analysis. If you use a DTM, then many obstructing objects will have been removed. However, as you yourself noted, Offset A/B is somewhat tricky, but this can be either completely ignored, or the analysis can be run with different values for Offset A/B, and then combined with a land-use model. This will allow ...


1

I guess you could achieve that with r.los. You could set different heights and see if there is a visibility. r.los elevation.dem out=los.025 coord=598869,4916642 obs_elev=25 max_dist=1000 r.los elevation.dem out=los.050 coord=598869,4916642 obs_elev=50 max_dist=1000 r.los elevation.dem out=los.100 coord=598869,4916642 obs_elev=100 max_dist=1000 r.los will ...


1

It looks like there's a problem in creating the vat when there are between 16 and 32 observers. I think the cell values themselves are correct, though. You can use the identify tool on the output raster to verify that. In any case, we'll take a look at it. For < 16 observers, you can use arcmap's 'relate' functionality directly with the vat and the orrt ...


1

The negative values were resulted from the Raster to Polygon conversion operation. This is because the conversion tool overflows when the input raster value is greater than 2 billion (approximately). I cannot explain such a large value in your Viewshed 2 output raster but maybe it relates to the number of observer points in your input feature class to ...


1

After several hours, I finally found the answer. It turns out that the scale on the map shows different values than the scale in the browser console (which I find odd), so I was adding the wrong values to the min/maxResolution. Working code: var test = new OpenLayers.Layer.Vector("xName", { strategies: [new OpenLayers....


1

Here is a list of all of the Keyboard Shortcuts and Tips that is provided with ArcGIS for Desktop. It looks like pressing spacebar while you have the layer selected will turn it off, and then pressing it again will turn it back on. This way you are free to roam the map and toggle the layer.


1

If you have access to 3D Analyst, there is a tool called Line of Sight from which you can directly create a Profile Graph that indicates which sections are visible and not from the observer points. See Creating a profile graph from line-of-sight results help file for details. Note the graphic output options are limited and may not allow you exactly ...


1

I had to do something rather like this for my masters thesis, but with much fewer observer and target points. I'm not aware of a reasonable way to create a complete raster of "visible area," at least not one that wouldn't take a long time. Repeatedly running Viewshed, once for each centroid of the raster's cells, would certainly work... but as you've, ...


1

In ArcGIS you can use the Viewshed tool (Spatial Analyst Tools > Surface). The Viewshed lets you calculate the surface locations visible to a set of points or lines (see the documentation).


1

I've got a bit of a workaround. While in layout view, I used the Microsoft Snipping tool (under Accessories) to "snip" pictures of the two additional data frames I was trying to overlay on my map. I saved the snips as pictures, then removed the additional data frames. I then added the snips back to my map as pictures where I had once had the additional data ...


1

This has been an issue for the past 2 versions of Desktop and no Service Pack addresses the issue. You can export to PNG as you have done and change the DPI to 300 for a better resolution.



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