# Tag Info

40

Every polygon has, at a minimum, four distinct "centers": The barycenter of its vertices. The barycenter of its edges. Its barycenter as a polygon. A GIS-specific "center" useful for labeling (usually calculated with undocumented proprietary methods). (They may accidentally coincide in special cases, but for "generic" polygons they are distinct points.) ...

33

Yes, there is an analytical solution for this problem. The algorithm you are looking for is known in polygon generalisation as "smallest surrounding rectangle". The algorithm you describe is fine but in order to solve the problems you have listed, you can use the fact that the orientation of the MAR is the same as the one of one of the edges of the point ...

29

To supplement @julien's great solution, here is a working implementation in R, which could serve as pseudocode to guide any GIS-specific implementation (or be applied directly in R, of course). Input is an array of point coordinates. Output (the value of mbr) is an array of the vertices of the minimum bounding rectangle (with the first one repeated to ...

26

Well, WebGL is promising but has few features now. You can have a look to the API and examples. From what I know, it is supported by FF4 and Chrome 9. You will find more about browsers compatibility on their website. Javascript libraries : http://cesium.agi.com/ and demos To explore (samples and tutorials) : A quite realistic 3D map using webGL and ...

25

To be honest the time frame you mentioned for the migration sounds really tight, especially if you want to research, test, evaluate and deploy! We have recently migrated from using ArcGIS as our desktop client to QGIS. While everything you have mentioned sounds possible the biggest issue I have found is managing the storage of Raster datasets, but like Nick ...

19

1) Analyse the areas outlined with the polygons and added buffers to some of them. Buffers are supported. For further help, we'd need to know what "analyse the areas" means. 2) Answer questions like: Does this kind of fish (represented by a layer of points) always occur near a certain rock type (represented by polygons or points). You can check if ...

17

What makes GIS stand out from graphic design and cartography is its use of quantitative reasoning and scientific and engineering principles. Let's see how this can work without getting bogged down in unnecessary calculations. Some Facts In GIS it is indeed useful to have a good intuition for lengths, areas, and even volumes. I'll get to that, but let's ...

16

1) For a full 3D GIS, the better is GRASS GIS, look at Screenshots of 3D data management or From drone-aerial pictures to DEM and ORTHOPHOTO: the case of Caldonazzo's castle, from example. Some examples (interactive: you can scale, rotate the representation and many other things) : DEM with 3D points: Draped raster on the DEM Draped geological map ...

15

To create cross section: use ArcGIS, MapInfo, etc. with point XYZ data projected on either south-north or east-west plane or use dedicated geological software to create the section (Geosoft Target, Leapfrog Mining, Rockworks, Datamine Studio, etc.) Might require some post-processing to manually add or adjust labels and text To create 3D topo/subsurface ...

14

ReadyMap might be another option. Here is an example (with a bonus of Leaflet integration!) [via @LeafletJS]: And one more with 3D overlay on the globe: More: demos, code. Update: The project seems to change its course rather drastically. ReadyMap is now: Free Data Service for ReadyMap and osgEarth Developers And the 3D globe application moved (...

12

From someone who is part of the "GE Generation" Atmospheric Data When you are visualizing atmospheric features, it is important to see a vertical profile of the atmosphere. Sub-surface data When working sub-surface (bore holes, or earthquakes as shown below). In the image below, magnitude is mapped to pin size, but depth is mapped (inverted) to ...

11

Not sure if standard GIS packages are going to give you what you need. You might have to get into 3D animation/visualization packages such as Vue (paid, but not too \$\$, maybe around \$1,000 US) or Blender (open source with HUGE community). I'd love to know what the NPS used to create the flyover you referenced. I'm currently struggling with getting real ...

11

I have created a couple of ArcGlobe videos in the past (~4yrs ago) that look to have about the same video quality as the NPS video you referenced. The key that I was told (and found to be true) was to: use keyframes to allow the software to create the appropriate transition between locations, capture the video at 4x - 8x times SLOWER than you want to ...

11

This is not the first time I encounter such question and generally it is asked by people outside of geospatial industry that are not familiar with cartographic theory or with practice needs (this is just my observation). As to the question: A "3d Globe" that you see on the screen is nothing less than just an Azimutal projection... And there is no such ...

11

3D globes and the like are very useful for quick visualization purposes. You can instantly see Global Level and Continental Level data, and spatial relationships and distances are easily understood. However if you think about it, you don't really need a Globe foe every such case. As SS_Rebelious has mentioned, a Globe on a Flat Screen, is basically an ...

11

As a geologist, my solution is GRASS GIS with nviz or Python from the Python Console with modules that allow the 3D representation (I never use commercial softwares and Globe or Horao, witch display QGIS layers on top of 3D globe, are inappropriate for geological 3D modelling): For GRASS GIS: Visualization and volumetric 3D examples For Python ...

10

I'm a little late to the party but here is another suggestion: http://potree.org/ It's an open souce, WebGL based point cloud viewer I've been working on for quite a while. == UPDATE == It can render large amounts of colored point clouds. LIDAR data without colors will be supported soon. Showcase: http://potree.org/wp/demo/ Source code: https://github....

9

I think both your points sum up the A to the Q quite well. Some examples where its useful: Flood Analysis Viewshed Analysis (including shadow analysis) Sub-terrain analysis (Geology, oil exploration) I think a key problem with 3D is the 'Google Earth Generation' (I just made that up), think that displaying everything in 3D is a good idea. This kind of ...

9

AutoCAD Map 3D can do floor plans - use it to create 2D and 3D floors - then floors lead to racks (servers) and racks go to device. Each level can be pulled out in to reveal floorplans with all the equipment locations.

9

Yes, it is possible but using a Python script in the console see For geologists: 3D geological boreholes I presented the scripts in visualizing 3D data (Z values) or data with z attribute: a solution or QGIS, représentation 3D des couches vectorielles (shapefiles dits 3D ou shapefiles avec attributs z) avec les modules Python Matplotlib ou Visvis à ...

8

Environmental investigations are inherently three dimensional. As a simple illustration of what some environmental data might look like, here is an image from a simple 3D GIS I created (using VRML) in the '90s. The box-like structures are buildings in an office park. The multi-colored "straws" display subsurface geologic readings taken every one to five ...

8

The term 2.5D is used instead of 3D because, although you have Z values, they are not taken into account when doing any of the spatial operations. Intersections, buffers, any of the spatial predicates (within, overlaps,etc) operate with by ignoring the Z value.

8

You need to fire up either ArcScene or ArcGlobe. They are typically installed with ArcGIS Desktop so I would imagine you already have them on your machine. If you don't have the 3D extensions (as mentioned by Brad in the comments) you could try ArcGIS Explorer which is a free viewer for both 2D and 3D data.

8

I've had a bit of experience with Rockworks (ver. 14.0) and am not incredibly impressed with it. While it's fairly easy to get data into the system, generating any kind of presentation quality (let alone publication quality) diagrams was extremely unintuitive. I gave up and drew the few cross-sections I needed by hand. I also came to realize that the cross-...

8

The Describe object also has the hasM and hasZ properties.

8

Thank you for clarifying your question as it was previously quite unclear. You can read a multiband raster using the stack or brick function in the raster package and assign the associated RGB values to an sp SpatialPointsDataFrame object using extract, also from raster. Coercion of the data.frame object (which results from read.csv) to an sp point object,...

7

Edit TIN. Arc Toolbox -> 3D Analyst Tools -> TIN Management -> Edit TIN Add in the polygon Feature class and choose for height field and hardclip for SF_Type

7

Easier then I thought (thanks to BenjaminGolder for the tip): ogr2ogr -f "DXF" Contours.dxf Contours.TAB -zfield Height Contours.TAB is the input MapInfo tab file.

7

One method is to create layers for each individual floor. You can turn layers on and off to see the respective floors. It probably would be a good idea to have a separate layer for the external walls or the footprint, which you can use while drawing internal walls at the different levels.

7

You've started in the right place, TopoToRaster will do what you've asked (create a seamless elevation model from contours). There are a lot of options and it can be a bear to get right, as the length of the overview implies. I found it helpful to read the documents for the source tool, ANUDEM, so I could understand more of the theory. Before that though, ...

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