How do YOU create various resolutions of the same map?

[liciobruno]

Most GISes have the ability to do various kinds of conditional symbolization based on scale. So you can tell it to do things like, if the scale is smaller than 1:100,000, only display cities with a population of at least 750,000. There are also tools to simplify linestrings and polygons so they are suitable for a particular scale, Inkscape does include a form of this.

Can you tell us some GIS which is simple to use and open source? I found Landserf, that is very simple, but it is not open source. Thanks.

[Redrobes]

Can you export the maps you create in viewing dale at full size (e.g., massive resolutions like 30000x___) or as tiles for use in googlemaps?

In the app you zoom the map so that you get on the screen what you would like to export. Then you can export the screen image as a BMP, PNG, or JPG and you can set the resolution. You can set that as either a DPI with image size in mm or inches and it will calculate the pixel size or you can set the pixel size directly. It will make the aspect ratio whatever you had the apps main map window set to.

You can easily export up to about 20,000 pixels wide but as you go higher then it will start to struggle because of the limitations of the file formats and the PC memory required to render the screen image. Generally, whatever the app, I would say that about 10,000 is the max anyone should export images at. I have various apps which start to generate rendering issues after about 14K square. Gimp and Photoshop are almost certainly able to cope tho. Remember that if a pixel is 4 bytes then 20,000 square is 4x20x20Mb or about 1.6Gb of image.

There is no option in the app to export a set of tiles which line up in a grid but there is an option to import a large image and have it break it up into tiles and import it. So it will import 20,000 pixel images into it. Using arrays of images from tile commercial sets, I have imported a 100,000 pixel square bitmap into it. Its slow of course but it will cope with it.

There is a setting where you can request the map as an image over a web page interface so that you can get a web browser to view the image with the correct URL. In the URL is the X,Y, zoom and image size. If you got a script to ask it for a set of tiles of the map and changed the X and Y values and saved out all of the images then you could get it to make lots of map tiles that way. That's not a trivial thing to do but it could be done. If your looking to serve up the map to players using a browser only then you can note that the app has a map web server built in for that purpose. But you would not be able to host that on the net as a web page hosted by some web company. Your machine running the app would be serving up the map images.

For googlemaps or some other similar map serving java I guess it comes down to the requirements of the images it needs to build up the page. A quad of 20K square images would get you a pretty deep zoom image for a google map tiling app to run with tho.

[Redrobes]

Can you tell us some GIS which is simple to use and open source? I found Landserf, that is very simple, but it is not open source. Thanks.

I have barely used it but QGis is open source free gis app.

[Hai-Etlik]

Can you tell us some GIS which is simple to use and open source? I found Landserf, that is very simple, but it is not open source. Thanks.

QuantumGIS and GRASS are the big names in FOSS desktop GISes, there are also uDig and OpenJUMP which I've heard are somewhat simpler, though I've never used them. For an easy way to install a range of FOSS GIS software on Windows, you might want to look at OSGeo4W.

[Redrobes]

Ahh yes, now you mention it I think QGIS is QuantumGIS. I did say I didn't use it much But yes thats the generic open source app that people head to.

[guyanonymous]

Redrobes,

Interesting. I really should check it out someday....it's only 'being stuck in the app' that's held me back since.

If I understand right, I can zoom out to encompass the whole map, export that at 20000pixels (or so) width, and it will include details that would resolve at that 20000 pixel resolution as though I'd had a 20000x____ window open and done a screen capture? (e.g., all the detail would be there)

I've found 30000x15000 or so is the max. size that compfortably works in -most- programs I've tried. Granted, I've not printed anything out that's 100 inches/50 inches, but you never know - I want to be prepared.

Do people need to own the viewingdale software to view the maps served on the web?

Thanks!

[Redrobes]

If I understand right, I can zoom out to encompass the whole map, export that at 20000pixels (or so) width, and it will include details that would resolve at that 20000 pixel resolution as though I'd had a 20000x____ window open and done a screen capture? (e.g., all the detail would be there)

That is correct. It is NOT like a screen capture scaled up to 20,000 pixels, its, as you say, as tho you had a 20,000 pixel screen so that detail which would be at the 1 pixel res is still there in the export. I had a video showing that somewhere. If I find it ill link it.

EDIT - Here it is:
http://www.viewing.ltd.uk/Temp/CG/VD...Demo1_xvid.avi
Its a bit long. Start half way through to see it save a 12,000 pixel image with 1 pixel detail.

Do people need to own the viewingdale software to view the maps served on the web?

Theres two modes of seeing a remote viewingdale map. You can a) use the VTT aspect of it where you locally generate the transferred map on your local copy of viewingdale. In that case you can modify the map locally and everyone gets the changes sent back. Its also super fast (realtime) scroll and zoom. For the VTT mode you need a copy. Or there is b) where you can set one master copy of viewingdale to act as a web server for the currently loaded map. In which case other people can use just a web browser only to request an image of the map at a set X,Y & Zoom and image size. In this case you can look at the map at different positions and scales but you cant edit it. You cant get a grid switched on or off or do very much. You just get an image. In a similar way that say google maps sends out tiles of maps to view but not edit. Note also this mode is served from the app not a web site. With your browser you need to ask for the image at your local IP address and do all the normal port forwarding for being a web server as opposed to normally being just a web client.

Using a combination of the two you can play the game with some people using a copy editing the map and have a couple of people using a web browser and they could use browser refresh to get a new image with changes made by the DM and other VTT players but he would have to request someone to move his characters icon.

If you have a static IP address and an always on windows box server then you could make web pages with links to your viewingdale web service so that you could have a wiki or a web based map and have links to map images which might change if you edited the map with the app. I.e. it would be a dynamic up to the minute view of the map areas without any need to FTP upload new static map images to a web site.

Hope that explains it.

[guyanonymous]

Thank you for the great explanation!

[sam]

Hello, a newbie here. I'd like to resurrect this thread.

Basically, I would like to use Google map API (or something that works similarly) to display both a country-level map,
and county, and then city-level detail. I made a largish map; and managed to slice it into tiles using the GMap Image Cutter.
The resulting Google map javascript-based API is very convenient. But even on my relatively small map,
the labels don't really work -- they are either too large or too small. Other problems have been noted upthread:
there is no feature discrimination, and roads (when I have them) and streams disappear at smaller scales.

Does anybody know a way to host zoomable maps on a generic web hosting site,
without a large investment in GIS software and data entry? Any pointers to further research would be welcome.

[Redrobes]

I believe with GMaps then you have various layers of image which the cutter chops up for you. I believe the idea is that you only render the text on the appropriate scale image but I would also imagine that a generic GMap tile cutter would be too dumb to know what bits to include and what to get rid of. So in order for you to have a set of tiles with text that is always the right size then you need to treat each layer of the map individually. The GMap cutter probably just takes one giant bitmap and chops it all up into the correct layers. I guess you could make several large map images with different text labels on them, GMap each of them and then use the tiles from a selection of the sets to make one that has labels that scale ?

With my app if the text is on the bitmap then it will do much the same and you can see that in the video in my previous post. However, if you put down text labels in the app not part of the background labels then you have the option to always keep them on, never show labels and then there is a third option of them fading out when too big. The best video I have of that is here:

https://www.youtube.com/watch?v=XKYU2gcsaoQ

where you need to look at the text as it zooms in.

In terms of hosting, my app can host a map but it needs a special web URL links to show it and over the web interface its not very dynamic. So basically whatever app option you choose you will either have to enter all of the labels so that they are in a format that it knows to fade them out or else you will need to use some kind of web package that can export the map to GMaps from a GIS style original that has all of the items in a database rather than on bitmaps.

From roads and and streams point of view you have the same problem. If you render each layer individually then you could plot them with a single line. If scaling from a large bitmap then they will get small and blend out of the image at small scale. If all you have is the bitmap then its a tough call to preserve small features at small scales. If you have it as a map element database then your into GIS domain again. So I guess the important missing info is what kind of map do you have and is it just a bitmap ?