Tag Info

Hot answers tagged

10

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.


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: ...


5

I cannot fully understand the code you have posted. When using the library OpenLayers, the usual programming pattern - as seen in the examples available at OpenLayers web page - consists on creating an instance of OpenLayers.Map that is stored in a global variable, so it is available to every function. Let us suppose that this variable is named map; then, ...


3

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

You should use separate OpenLayers.Layer.Vector object for each WFS-layer. For example: var mylayer_1 = new OpenLayers.Layer.Vector("My Layer 1", { .... featureType: "mylayer_1", ... }); var mylayer_2 = new OpenLayers.Layer.Vector("My Layer 2", { .... featureType: "mylayer_2", ... });


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

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

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

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: ...


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.


1

You can use an offset for one of the two routes. You find the option for each line style.


1

Edit: My first answer was totally off base. This one should be more helpful. The short version: You're correct that the onclick function is being called twice. The reason this is happening is that you're calling drupal.attachBehaviors() too many times - once in the drupal code, once in openlayers.js, and then once in openlayers_behavior_popup.js. If you ...


1

In GRASS GIS version 7 (actually not stable) there is the command r.skyview (based on the command r.horizon, available also in the stable GRASS v.6). It reads a raster image representing a terrain model, with pixel value corresponding to terrain feature heights (e.g. building heights) and calculates, for each pixel, the "skyview factor". You need first to ...



Only top voted, non community-wiki answers of a minimum length are eligible