I need to create whole-sky maps, but Google Earth in Sky mode has limited "zoom out." Is it possible to create an orthographic map projection with Google Earth (or, for that matter, MS Virtual Earth)? Really any of the standard projections will do, although it would be nice to have options.
Of course, I could render the projection statically and then paint my KML layer on top of it, but the ideal use-case would allow the user to add additional KML layers, zoom in and out, etc.
No they don't. This was a bone of contention in a series of articles I wrote just over a year ago. I wasn't after an orthographic projection, but equal area projections. People insist on plotting geostatistical data on non-equal area projections, mainly because they don't know any better and/or Google Maps, Bing Maps, etc do not offer any alternatives.
my demo of how it should be done used OpenLayers which can support various different map projections.
I haven't seen OpenLayers being used for star maps, but I can't see any fundamental reasons why it should not work. Also the star data is generally available in the public domain, I believe.
Related
I have coordinates, which are assigned a corresponding geohash in my database. Now I want to retrieve all of the coordinates within two bounding coordinates (top right and top left corner). How can I do that properly?
I tried getting the geohash that fits both of those bounding coordinates, but this solution does not work when they are in completely different regions of the world (so they are not sharing anything in common).
Is there a better way to do that?
Thanks for your help
Unfortunately, this isn't something you can do out-of-the-box with datastore / App engine. (There are no built in spatial queries.)
For early prototyping, etc., you can do it the hard way - retrieve all the rows, and discard the ones not meeting your query in code. Obviously, probably not viable with real production data.
See related question Query for Entities Nearby with Geopt for some possible production solutions.
I understand the concept of LOD but I am trying to find out the negative side of it and I see no reference to that from Googling around. The only pro I keep coming across is that it improves performance by omitting details when an object is far and displaying better graphics when the object is near.
Seriously that is the only pro and zero con? Please advice. Tnks.
There are several kinds of LOD based on camera distance. Geometric, animation, texture, and shading variations are the most common (there are also LOD changes that can occur based on image size and, for gaming, hardware capabilities and/or frame rate considerations).
At far distances, models can change tessellation or be replaced by simpler models. Animated details (say, fingers) may simplify or disappear. Textures may move to simpler textures, bump maps vanish, spec/diffuse maps combines, etc. And shaders may also swap-put to reduce the number of texture inputs or calculation (though this is less common and may be less profitable, since when objects are far away they already fill fewer pixels -- but it's important for screen-filling entities like, say, a mountain).
The upsides are that your game/app will have to render less data, and in some cases, the LOD down-rezzed model may actually look better when far away than the more-complex model (usually because the more detailed model will exhibit aliasing when far away, but the simpler one can be tuned for that distance). This frees-up resources for the nearer models that you probably care about, and lets you render overall larger scenes -- you might only be able to render three spaceships at a time at full-res, but hundreds if you use LODs.
The downsides are pretty obvious: you need to support asset swapping, which can mean both the real-time selection of different assets and switching them but also the management (at times of having both models in your memory pipeline (one to discard, one to load)); and those models don't come from the air, someone needs to create them. Finally, and this is really tricky for PC apps, less so for more stable platforms like console gaming: HOW DO YOU MEASURE the rendering benefit? What's the best point to flip from version A of a model to B, and B to C, etc? Often LODs are made based on some pretty hand-wavy specifications from an engineer or even a producer or an art director, based on hunches. Good measurement is important.
LOD has a variety of frameworks. What you are describing fits a distance-based framework.
One possible con is that you will have inaccuracies when you choose an arbitrary point within the object for every distance calculation. This will cause popping effects at times since the viewpoint can change depending on orientation.
I need to create dash boards showing geographic regions and show sales, hot spots etc on a map.
What have you tried and what do you recommend?
I like the look of both Fusion Charts and Dundas
I will be using asp.net for the site but any control's or library's including flash or javascript are good options.
Most important is the look and feel followed by functionality in South Africa.
After my last post looking for commercial mapping solutions, it looks like they are very expensive and now I am investigating alternatives to full mapping solutions.
thanks
Have a look at http://www.geoext.org/examples.html#examples a JavaScript library based opn top of OpenLayers and ExtJS.
You can limit the bounds of your map to different regions, have several pop-up maps etc.
Have a look at the OpenLayers API on what datasources you can use. GeoJSON or KML are probably easiest if you want to avoid server-side map serving software.
I'm trying to generate a KML file to display a set of features scattered around the UK. I would like the features to be grouped together at higher zoom levels, ideally displaying as an icon with a count of the number of features, so that users can see clusters of features easily.
Essentially I'm trying to do something along these lines, but in Google Earth, not Maps.
Can anyone point me in the right direction. I'm a bit of a newbie with KML :-)
Cheers,
RB.
ANSWERS :
My own research suggests I can do what I want using Regions to define bounding boxes for certain features.
It has also been suggested I should do this using network links, which I'm going to investigate as I think it's a better match for other reasons too.
Is this a standalone KML file? Or the KML returned as data for a network link?
In the first case I'm not sure this is even possible. I have seen layer transparency change with "camera altitude", so perhaps something like this is also possible on features? Then you could add both the single features and the groups features into the same KML file and make them visible based on "distance to camera"? Could be a new KML feature I missed, but you'd have the check the KML specification.
In the second case, you just return KML that matches the given network link viewport information. Based on the bounding box you get, you can subdivide that box into a grid and cluster per box. If you have one feature in a box, return the feature. If you have more than one in a box, return just a "grouped feature" for that box. The clustering will then automatically change when the user moves around in Google Earth: after each camera change your network link URL is called again and you again do feature selection and clustering with the given bounding box viewport. This makes your clustering dynamic.
Does this help?
I work for a ticketing agency and we print out tickets on our own ticket printer. I have been straight coding the ticket designs and storing the templates in a database. If we need a new field adding to a ticket I manually add it and use the arcane co-ordinate system to estimate where the fields should go and how much the other fields need to move by to accomodate new info.
We always planned to make this system automate with a simple (I stress the word simple) graphical editor. Basically we don't forsee tickets changing radically in shape any time soon, we have one size of ticket and the ticket printer firmware is super simple because it's more of an industrial machine, it has about 10 fonts and some really basic sizing interactions.
I need to make this editor display a rectangle of the dimensions by pixel of the tickets (can even be actual size) and have a resizable grid which can toggle between superimposition and invisibility on top of the ticket rectangle and represented by dots rather than lines.
Then I want to be able to represent fields by drawing rectangles filled with the letter "x" that show the maximum size of the field (to prevent overlaps). These fields should be selectable, draggable and droppable in a snap to grid fashion.
I've worked out the maths of it but I have no idea how to draw rectangles and then draw grids in layers and then put further rectangles full of 'x'es on top of those. I also don't really know much about changing drawn positions in accordance with mouse events. It's simply not something I've ever had to do.
All the tutorials I've seen so far presume that you already know a lot about using the draw objects and are seeking to extend a basic knowledge of these things. I just need pointing in the direction of a good tutorial in manipulating floating objects in a picturebox in the first place.
Any ideas?
For those of you in need of a guide to this unusual (at least those of us with a BIS background) field I would heartily endorse:
https://web.archive.org/web/20141230145656/http://bobpowell.net/faqmain.aspx
I am now happily drawing graphical interfaces and getting them to respond to control inputs with not too much hassle.