Technical Ramblings

So, as a result of Custom Projection 6: Google Projection, I got pinged by SharpGIS on IRC, and told that the projection I had there was wrong.

He helped me understand what he was using, and I let him know it still wasn’t helping me. So I set up a Virtual Earth + TileCache demo, and he helped me find the missing piece, in the proj4 FAQ:

In this case, and many other cases using spherical projections, the desired approach is to actually treat the lat/long locations on the sphere as if they were on WGS84 without any adjustments when using them for converting to other coordinate systems. The solution is to “trick” PROJ.4 into applying no change to the lat/long values when going to (and through) WGS84. This can be accomplished by asking PROJ to use a null grid shift file for switching from your spherical lat/long coordinates to WGS84.

+proj=merc +a=6378137 +b=6378137 +lat_ts=0.0 +lon_0=0.0 +x_0=0.0 +y_0=0 +k=1.0 +units=m +nadgrids=@null +no_defs

The key here was the +nadgrids=@null, which I’d never seen anywhere before.

The end result?

• Fixing my OSM Tiles
• WMS and TMS overlaid in OpenLayers, as described in an email
• A slightly better understanding of what I didn’t understand for so long.

So. Nice. To not feel lost anymore.

Three cheers for sharpgis! Hooray hooray hooray!

As of 5PM today, I will be unavailable on the web until July 9th. I’m going on a honeymoon, and I’m leaving my computer offline for the entire trip. (Yes, I am a workaholic. Heck, I committed to OpenLayers less than 2 hours before my wedding.) So, although I will be at home slightly more than that, you should not expect to hear from me until July 9th. If you have something that requires my urgent attention, please get it to me today

My actual honeymoon will include a stay at the Mount Washington Hotel, in the White Mountains of New Hampshire. Not to pat myself on the back too much, but I think I’ve earned it

Don’t break anything while I’m gone!

Went out for a late night walk tonight: though my path was a bit unclear, I think I made a decently accurate map:

Walking around MIT

If you hover over the circles, you’ll see points of interest along the route. I recommend zooming into the main MIT building, to see the confused meandering I was forced to.

This demo uses OpenLayers, TileCache, and FeatureServer. It was created entirely via a web interface.

I think from now on, I’m not going to try to answer questions on mailing lists which don’t follow the guidelines of “How to Ask Questions the Smart Way“. I spend way too much time trying to extract information that’s needed to solve any
problems. Obviously, in some cases, it’s hard to know which information is important, but with two open source projects with growing user populations, it’s very hard for me to take the time to coax every person through getting the information that is important to solving problems.

I think it is a sign of the growth in popularity of the OpenLayers and TileCache projects that I’ve come to this stage — it’s only when projects reach a certain level of maturity that people start asking enough questions that I don’t feel like I can just answer everything. Certainly, for the first 6 months of the OpenLayers project, I never felt that answering questions on the mailing list was something that was a burden to do, but over the past couple months, it’s been an increasing level of traffic from users who haven’t taken the time to investigate the cause of their problems fully. I think the time has come to stop devoting as much energy to solving *every* problem, and instead solve the problems that can’t be solved by other people.

Of course, an additional step is to work to create a forum in which users can offer cash to solve their problems — you put up a question, with a cash bounty on it, and you either increase the amount of money you’re willing to spend to get your question answered, or you answer it yourself.

This seems like the kind of thing that there should already be software to do. I’ve never heard of any, though. I wonder why that is. Probably something obvious I’m missing.

OpenLayers now has its own blog.

Thank the creation of Planet OSGeo for the final inspiration to actually put it together.

So, last week was an OpenLayers hack week. One of the things that we did was make adding support for new vector formats trivial. Instead of modifying several parts of the code, you only need to create two functions: a ‘read’, which takes a set of data — XML, strings, Javascript object, what have you — and returns a list of OpenLayers.Feature.Vector objects, and a ‘write’ which does the reverse — takes a list of objects and returns a string or object or XML.

To prove this, I set out to write some additional vector format support last night. I decided to add one read, and one write.

• Read: KML. I added support for KML point display in about 20 minutes, including the time to find data and write a demo HTML page loading some example data. Adding LineString support was another 15 minutes.
• Write: GeoRSS. Support for writing georss:simple points, lines, and polygons was simple… once I found data. I asked for a live example, and was unfortunately unable to find any valid line data outside the GeoRSS website, so I just generated something that was as close as I could come to the examples. I’m lazy, so the export is just RSS 2, and I’m sure that someone will come along and criticize it, but that’s one of the benefits of Open Source: Anyone can offer up a patch. Time from when I created the file stub to when I committed the code was 27 minutes, again, including a demo.

Altogether, the Format support in the new OpenLayers is pretty cool. Because of the way it’s built, I can even do something that is pretty damn ridiculous: Import KML, and export GeoRSS (or GML), all from the browser. Certainly, this is an incredibly crazy thing to do, but OpenLayers is a pretty crazy project.

I’m convinced that there’s nothing in the code that would make it difficult for someone who’s comfortable working with Javascript to write support for any simple-to-parse format. Now, to get the code back to trunk and get the patches rolling in.

Earlier this evening, Atrus pointed out that DC has a bunch of cool data in their GIS Data Catalog. I decided I would play with it a bit and see what I could come up with.

I grabbed the Street Centerlines, played with it in QGIS to do a bit of cartography, and then (eventually) got it exported to a MapServer .map file (which describes styling info). I was then able to set the file up in MapServer, serve it out to OpenLayers, and then to stick TileCache in the mix. The result isn’t the prettiest thing in the world, but it works.
After going through it once, I decided I’d go through it all again, to see how long it took.

• 12:15AM: Open Firefox to the DC Data Catalog to find some data to map.
• 12:16AM: Pick out Structures Polygons.
• 12:17AM: Download complete, open QGIS
• 12:18AM: Open file in QGIS
• 12:19AM: Save QGIS project file, save map file from project file
• 12:20AM: Copy both shapefile and mapfile to server
• 12:21AM: Tweak mapfile: adjust PNG output to not be interlaced (for TileCache usage), change background color
• 12:22AM: Test mapfile in mapserv CGI. Find out I misspelled something, fix it.
• 12:23AM: Edit TileCache config to add new layer information.
• 12:24AM: Copy an existing tile URL, ensure that it works in TileCache with the different layer.
• 12:25AM: Edit OpenLayers config to include additional layer
• 12:26AM: Edit OpenLayers config to include layerswitcher.
• 12:27AM: Marvel at the result

In less than 15 minutes I was able to turn a dataset into a browsable, lazily cached web viewable data set, using qgis, OpenLayers, and TileCache. Not bad at all.

A bit more than a year ago, when I was just learning how to use the Google Maps API, I put together a patch for the OpenGuides software, adding Google Maps support. It seemed the logical way to go: It wasn’t perfect, since Google Maps are obviously non-free, but it seemed like a better way to get the geographic output from OpenGuides out there than anything else at the time.

Since I did that, I’ve learned a lot. Remember that 18 months ago, I’d never installed MapServer, had no idea what PostGIS was, and didn’t realize that there were free alternatives to some of the things that Google had done. Also, 9 months ago, there was no OpenLayers, or any decent open alternative to the Google Maps API.

In the past 18 months, that’s all changed. I’ve done map cartography, I’ve done setting up of map servers, and I worked full time for several months on the OpenLayers project. Although my direction has changed slightly, I still work heavily with maps on a daily basis, and spend more of my time on things like TileCache, which lets you serve map tiles at hundreds of requests/second.

So, about a month ago, I went back to the Open Guide to Boston, and converted all the Google Maps API calls to OpenLayers API calls. The conversion took about an hour, as I replaced all the templates with the different code. (If I was writing it again, it would have taken less time, but this was my first large scale open source Javascript undertaking, long before I gained the knowledge I now have from working with OpenLayers.) In that hour, I was able to convert all the existing maps to use free data from MassGIS, rather than the copyrighted data from Google, and to have Google as a backup: a Map of Furniture Stores can show you the different. You’ll see that there are several layers — one of which is a roadmap provided by me, one from Google — and one from the USGS, topographic quad charts.

It’s possible that some of this could have been done using Google as the tool. There’s nothing really magical here. But now, the data in the guide is no longer displayed by default on top of closed source data that no one can have access to. Instead, it’s displayed on top of an open dataset provided by my state government.

This is how the world should work. The data that the government collects should be made available to the people for things exactly like this. It shouldn’t require a ‘grassroots remapping’: There are examples out there of how to do it right. I find it so depressing to talk to friends in the UK, who not only don’t have the 1:5000 scale quality road data that Massachusetts provides, but doesn’t even provide TIGER-level data that the geocoder on the Open Guide to Boston uses.

Free Guides, with Free Maps. That’s the way it should be. The fact that it isn’t everywhere is sad, but at least it’s good to know that the technology is there. Switching from Google to OpenLayers is an easy task — it’s what happens next that is a problem. You need the data from somewhere, and it’s unfortunate that that ’somewhere’ needs to be Google for so many people. I’m thankful to MassGIS and to the US Government for providing the data I can use, and to all the people who helped me learn enough to realize that using Google for everything is heading the wrong way when you want to not be beholden to a specific set of restrictions placed on a corporate entity.

So it seems clear to me that the Pipes application is a step in a really cool direction. I don’t know if there’s anything incredibly innovative in the idea of making programming easy, but Yahoo! has gone a long way towards the goals that other people have put into place. Ning thought that letting people code would be the way forward: give them a sandbox, let them copy paste, and they’ll build applications. The idea was right: there are a lot more people out there who want to be builders that aren’t. It turned out that the people who want to be builders didn’t have the skill level that they needed to build PHP code, even with mix/match and copy/paste.

Yahoo! Pipes is the followthrough on that idea: make it possible for people to take a set of input, and get a set of output, passing it through multiple filters.

The next step is obvious: Let people turn the filter settings into a web page, with the output being another web page. Search for all content 5 miles from a given Craigslist location: Take the user input as drop down boxes or something in an HTML form, and make the output a Yahoo! Map. Boom: you’ve turned everyone who can create a pipe into a web application builder. Stick ads along the bottom, and you’ve done one of the things that Ning tried to do: make money off applications in the same way that so many have made money off content.

I’m sure that Yahoo! already has this in mind, whether they’ve written about it or done it yet or not. It’s only a matter of time. It does make me wonder if someone could build something that did this without needing Yahoo! to do it… It seems like at the moment it would require altering a pipe on the fly, which I don’t see a way to do, so either there needs to be a further API, or we’ll all just need for it to get done

Update: Looking today, you can control the input of text inputs from the URL that you fetch the RSS with. This means that I can go ahead and build the pipe thingy for my own pipes as is. That’s pretty cool. I’ll show one with MetaCarta stuff on Monday.

Perhaps I’ll build an OpenLayers based Yahoo Pipe output viewer. It wouldn’t be that different from the GeoRSS viewer… but it would need a way to visualize non-Geo content. Ponder ponder.

Recently, an OpenLayers contributor posted about his recent development of an interactive zoom for OpenLayers:

Animated Zoom Demo (Drag the scroll bar up and down to see the feature in action.)

I love this demo, because it’s a demonstration of one of the things you can do with OpenLayers that you simply can’t do with Google Maps. Looking forward to seeing OpenLayers work with the developer in question to integrate his patches and hard work.