GIS Data Formats and My Stubborn Opinons

Taking this break I’ve been looking over my spatial data and trying to figure out how to best organize it. The largest public project I manage is the GeoJSON Ballparks and this one is easy to manage as it is just a Git repository with text files. GeoJSON makes sense here because it is a very simple dataset (x/y) and it has been used for mapping projects mostly which makes the GeoJSON format perfect. I used to maintain a Shapefile version of it in that repository but nobody ever downloaded it so I just killed it eventually.

But my other data projects, things I’ve mapped or worked on the past are in a couple of formats:

VECTOR

  • Shapefile
  • File Geodatabase
  • Personal Geodatabase
  • GeoJSON
  • KML
  • SpatiaLite

RASTER

  • TIFF (mostly GeoTIFF)
  • Esri Grid

Now you can tell from some of these formats, I haven’t touched these datasets in a long time. Being Mac centric, the Personal Geodatabase is dead to me and given the modification dates on that stuff is 2005-2007 I doubt I’ll need it anytime soon. But it does bring of the question of archival, clearly PGDB isn’t the best format for this and I probably should convert it soon to some other format. Bill Dollins would tell me GeoPackage would be the best as Shapefile would cause me to lose data given limits of DBF, but I’m not a big fan of the format mostly because I’ve never needed to use it. Moving the data to GeoJSON would be good because who doesn’t like text formats, but GeoJSON doesn’t handle curves and while it might be fine for the Personal Geodatabase data, it doesn’t make a ton of sense for more complex data.

This is as close to a shapefile icon as I could find, tells you everything doesn’t it?

I’ve thought about WKT as an archival format (specifically WKB) which might make sense for me given the great WKT/WKB support in databases. But again, could I be just making my life harder than it needs to be just to not use the GeoPackage? But there is something about WKT/WKB that makes me comfortable for storing data for a long time given the long term support of the standard among so many of those databases. The practical method might be everything in GeoJSON except curves and those can get into WKT/WKB.

Raster is much easier given most of that data is in two fairly open formats. GeoTIFF or TIFF probably will be around longer than you or I and Esri grid formats have been well support through the years making both fairly safe. What are some limits to data formats that I do worry about?

  1. File size, do they have limits to how large they can be (e.g. TIFF and 32-bit limit)
  2. File structure, do they have limits to what can be stored (e.g. GeoJSON and curves)
  3. File format issues (e.g. everything about the Shapefile and dbf)
  4. OS centric formats (PGDB working only on Windows)

I think the two biggest fears of mine are the last two, because the first to can be mitigated fairly easily. My plan is the following; convert all vector data into GeoJSON, except where curves are required, I’m punting curves right now because I only have 3 datasets that require them and I’ll leave them in their native formats for now. The raster data is fine, TIFF and grid is perfect and I won’t be touching them at all. The other thing I’m doing is documenting the projects and data so that future James (or whomever gets this hard drive eventually) knows what the data is and how it was used. So little of what I have has any documentation, at least I’m lucky enough the file names make sense and the PDFs help me understand what the layers are used for.

One thing I’ve ignored through this, what to do with those MXDs that I cannot open at all? While I do have PDF versions of those MXDs, I have no tool to open them on Mac and even if I could, the pathing is probably a mess anyway. It bring up the point that the hardest thing to archive is cartography, especially if it is locked in a binary file like an MXD. At least in that case, it isn’t too hard to find someone with a license of ArcMap to help me out. But boy, it would be nice to have a good cartography archival format that isn’t some CSS thing.

10 Years Ago on Spatially Adjusted – “Ron Lake – What is KML?”

10 years ago, Google Earth was still somewhat unknown.  It had its big coming out party with a natural disaster1 and people started doing amazing things with it.  If there was one person back in 2005 that knew XML spatial formats, it was Ron Lake.  He wrote a commentary on KML 10 years ago this week.  I for one read his article with 10 years of time to think about they implications of KML and see why from his perspective KML was not able to handle his needs.

Back then we all thought KML was the future and there wasn’t much that couldn’t be done.  I think now we all realize that KML is the new PDF except we knew that 10 years ago.  XML of course is never the answer…

  1. Katrina 

SpatialTau v1.2 – Tilting at the Shapefile

SpatialTau is my weekly newsletter that goes out every Wednesday. The archive shows up in my blog a month after the newsletter is published. If you’d like to subscribe, please do so here.


Tilting at the Shapefile

Now I’m sure if I went back to my blog and searched for how many times I’ve tried to kill off the shapefile even I would be surprised at how many times I’ve blogged about it.  Thus it seems about for the second newsletter I’ve ever written to focus on the “Shapefile Problem”

The Problem

So what exactly is this problem?  I mean what is so bad about a well supported, somewhat open file format?  I’ve told this story before but it never hurts to repeat.  My dad was borrowing my laptop a couple years ago and commented about all these DBF files all over my desktop.  He wondered why on earth would I have a format that he used in the late 80’s and outgrew because of it’s limitations.  Well I proceeded to explain to him the shapefile and how it worked and he just laughed.  That’s right, my 72 year old dad laughs at us wankers and our shapefile.  The DBF is only half the problem with the shapefile.  It doesn’t understand topology, only handles simple features (ever try and draw a curve in a shapefile?), puny 2GB file size limitation and not to mention you can’t combine points, polygons and lines in one file (hence every shapefile name has the word point, line or poly in it).

Oh and it’s anywhere between 3 and 15ish file types/extensions.  Sure 3 are required but the rest just clutter up your folders.  I love the *.shp.xml one especially because clearly they thought so much about how to render metadata.  If I had a penny for every time someone emailed me just the *.shp file without the other two I’d be a rich man.  Heck just the other day I got the *.shp and *.dbf but not the *.shx.  Just typing the sentence makes me cringe.

The Contenders

  1. The File Geodatabase (FGDB):  Esri’s default format for their tools.  It’a spatial database in a folder format.  The less mentioned about the Personal Geodatabase, the better.  But unlike most companies in the past 5 years, it isn’t built on SQLite, but Esri proprietary geodatabase format.  There isn’t anything inherently wrong with Esri taking this path but it means you’re stuck using their software or their APIs to access the file format.  To me this severely limits the FGDB to me an interchange file format and I think that is perfectly fine with Esri as they don’t really care too much if the FGDB doesn’t work with other’s software.  I’d link to an Esri page that describes the FGDB but there isn’t one. It’s a secret proprietary format that even Esri doesn’t want to tell you about.
  2. SpatiaLite: SpatiaLite has everything going for it.  It’s a spatial extension to SQLite which means at its core it’s open.  It’s OGC Simple Features compliant.  It is relatively well supported by GIS software (even Esri technically can support it with the help of Safe Software).  Plus it supports all those complex features that the shapefile can’t.  Heck OGC even chose it as the reference implementation for the GeoPackage (assuming people still care about that).  Heck supports rasters too!  But honestly, SpatiaLite was released in 2008 and hasn’t really made a dent into the market.  I can’t ever remember downloading or being sent a SpatiaLite file.  I’m guessing you can’t either.  I mean we all want a format that is similar to PostGIS and easily transferable (one file).  On paper that’s SpatiaLite.  But I think we have to chalk this up as Esri not supporting the format and it is relegated to niche use.
  3. GML/KMLRon Lake probably loves I grouped these together but honestly they’re so similar in basic structure I’ve really just left them together.  My company uses KML quite a bit to share georeferenced photos.  That’s about it, pretty low use.  There is a ton of KML out there but it is mostly points.  There might be a ton of GML out there but I’m not Ron Lake.  KML is nice in the sense it has visualization included in the spec (you can make a line yellow) but it isn’t enough to get excited about.  It’s an OGC standard but as with SpatiaLite that doesn’t really seem to matter in the real world.  Don’t even try and use a different projection.  They have their use in specific cases but the limits of the formats means you’ll never see it being an interchange format.  Plus XML?  Oh and feel free to email me how GML is powerful because it supports OGC Simple features, I’ll still include it with KML.
  4. GeoJSON: It’s an open standard, so open in fact that OGC isn’t involved.  That’s a huge plus because mostly standards organizations do is make complex file formats for simple uses.  That’s not what GeoJSON is.  It can be many types of projections, it can be points, polygons and lines (with variations of many), it supports topology with the TopoJSON format and it’s JSON so it’s human readable.  But alas it isn’t supported by Esri so we run into the same problem as SpatiaLite.  BUT, Esri has shown interest in GeoJSON so there is hope that it will be well supported soon.  As with the shapefile/KML and unlike SpatiaLite it won’t support curves and other complex geometry or rasters and never will.  Thus it is not well suited as a shapefile replacement.
  5. Well Known Text (WKT): This comes out of the OGC and is used by software such as PostGIS for storage.  WKT supports lots of geometric objects (curves!) and TINs.  I’ve never been limited by WKT for vector files (you can almost feel where the end of this is going though) and many spatial databases from PostGIS and Oracle to SpatiaLite and SQL Server use the WKB (Well Known Binary) equivalent to store information.  But alas, we still don’t support rasters.  It’s a vector format for vector data.  SpatiaLite and the File Geodatabase both support rasters.

There are many other formats but I think these are the only ones that really have any traction.  I could list formats such as GeoTIFF and say you could use that for rasters but you are limited to 4GB of data.  The vector guy in me wants to just say the heck with it all and use GeoJSON and WKT to solve the problem but given I’m still writing about this subject in December 2014 neither is a good solution.  We’re left with one simple truth…

The Verdict

The shapefile will outlive us all.  Unless Esri stops supporting it with their software at the same time as QGIS, Autodesk, etc it will continue to be the format that everyone uses.  In 2014 I’d wager 80% of all production geospatial data (I’m sandbagging here, probably this number is 95%) is stuck in the shapefile format where it resides comfortably.  Personally I’m a big fan of GeoJSON but I’ve started to get back into WKT lately and love the complex geometry support. If there is one thing I’ve learned in the past 20 years of “professional GIS” I’ve done, the shapefile is king.

Issues with 3D models in Google Earth

Link – Google Earth St Paul’s and Digital Elevation Model

I’ve been focused on using Google Earth for a GIS viewer, but some others have been looking at using it for 3D models.

…problems have arisen with the Google Digital Elevation model (DEM). St Paul’s is located on a natural hill in London but the resolution of the DEM is not enough to compensate for the building size and structure.

By default Google Earth drapes the models to the landscape, resulting in a model which slopes, losing the straight lines and introducing distortion. To get around this it can be placed absolute to the ground, resulting in a 11 metre difference between the front and the rear of the building – as it sits on a hill. This has been compensated for in the model but it throws out the actual building height relative to the skyline.

Interesting. I’ve noticed some problems with a x/y shift going on when I try and create 3D views of buildings in Google Earth, but it looks like those who work with 3D Studio Max and ArcScene are also left wondering how/if Google might fix their issues with Google Earth.

Issues with 3D models in Google Earth

Link – Google Earth St Paul’s and Digital Elevation Model

I’ve been focused on using Google Earth for a GIS viewer, but some others have been looking at using it for 3D models.

…problems have arisen with the Google Digital Elevation model (DEM). St Paul’s is located on a natural hill in London but the resolution of the DEM is not enough to compensate for the building size and structure.

By default Google Earth drapes the models to the landscape, resulting in a model which slopes, losing the straight lines and introducing distortion. To get around this it can be placed absolute to the ground, resulting in a 11 metre difference between the front and the rear of the building – as it sits on a hill. This has been compensated for in the model but it throws out the actual building height relative to the skyline.

Interesting. I’ve noticed some problems with a x/y shift going on when I try and create 3D views of buildings in Google Earth, but it looks like those who work with 3D Studio Max and ArcScene are also left wondering how/if Google might fix their issues with Google Earth.

Export to KML Extension for ArcGIS 9.x

Link – Export_to_KML_V10

Export to KML is an extension developed for ArcGIS 9.x by the City of Portland, Bureau of Planning. The extension allows ArcGIS users to export any dataset in “keyhole markup language” [KML] format for viewing in the free Google Earth data viewer. Any point, polyline, or polygon features, in any defined projection, can be exported. Features can be “grouped” by an attribute for creating categorical symbology in Google Earth. Features can also be exported as 2-dimensional features, or “extruded” by an attribute (or, in the case of true 3D features, by z-value).

Kevin Martin over at the City of Portland Bureau of Planning just uploaded a new extension to export any dataset to KML.

Export2KML

Structure height

One problem with all these great tools for KML export is that they have all chosen to use the Google Earth icon on their toolbar. Kind of makes it hard to remember which one is which huh?

Kml extensions

Ron Lake – What is KML?

Link – What is KML?

One could easily create a GML representation for , treating it as a GML feature. So far so good. What about using KML to represent other geographic features? It seems unsatisfactory to say that all geographic features need to be represerted using . How would we encode say a building with a polygonal extent, a number of floors, a height, a position, a type (e.g. Church, Police Station etc), and the date when the building was erected.

Defenders of GML are begining to take a closer look at KML.

KML Home Companion 2.0

Link – KML Home Companion (new 2.0)

Jim Cser emailed me and let me know that KML Home Companion 2.0 is now available. The new features include
on-the-fly Lat/Long conversion, and color picker tools. Jim is also kind enough to include the source VB code with his distribution. One thing I really like about KML Home Companion is that it is so simple to use. I’m stuck at home this morning, but when I get in later I’ll post some screen shots.

More GIS to KML tools showing up in ArcScripts

Link – KML Home Companion 0.9

“This is an ArcMap extension designed to aid in creating KML format files for use in Google Earth. I tried to create the simplest program that would do the job, so there is not much in the way of error checking or fancy features. Please feel free to modify the code, report bugs, or to make suggestions for future releases.”

Link – Shape 2 KML

Shape 2 KML (Google Earth)
Version 1.0.1
Bug fixed encoding name and description”

ArcMap Feature Layer to KML

Link – VBA code for Google Earth KML paths

ArcObjects VBA code to take a feature layer, split it up into line segments, and then generate a valid KML file. It’s pretty basic, and you have to hard code some values, but it does the job. It will work with either lines or polygons, and it shouldn’t matter whether it’s a shapefile or a coverage. Just make sure that your layer is projected into lat/long first.

Looks like Jim’s code is now on ArcScripts.