Following on from my post pointing to free downloadable map data for the UK and Roman period, and yesterday’s post giving walk-throughs on importing three types of file available from theDigiMap to ArcMap, I’ve got another file type to discuss:
Profile and Panorama Contour vector data (NTF files)
Edina Digimap are in the process of moving all map data downloads to their main ‘Data Downloads’ interface, where you can select multiple types all on the same screen, order them, and receive an email with a link to download them all in a zip file. If you look under the ‘Land and Height Data’ section, you’ll see two options for contour data (those cool looking contour lines on maps): Profile and Panorama. Profile is the really minutely mapped one, Panorama the slightly easier overview – though they are both really densely packed with information.
These files are delivered as NTF files, which are not viewable in ArcMap 10.1 nor QGIS (the free open-source mapping software). Once again, the solution to this problem for ArcMap is to use the Productivity Suite extension, which I don’t have, so we’re going to be jumping through hoops a little this time. The solution I present here isn’t fool-proof – in fact, it doesn’t actually work all the time, for reasons I haven’t been able to fathom. As I can’t actually open the original NTF files I’m downloading, I don’t know if the problems with this work-around are due to the NTFs (which I know are sometimes missing pieces) or due to the software I’m using, or my own actions.
However, this remains the only functional solution to opening NTF files in ArcMap (and QGIS) that I’ve found, so I present it here:
Getting NTF files into ArcMap
First thing’s first: you’re going to need to convert the NTF files into MIF files. I use NTF2MIF, a free piece of software you can download here. It only has one screen and there’s limited options. Simply load in all the NTF files (it seems to be able to cope with lots in one go), and select the Output Option: Merge tiles or Separate Tiles. Both of these work, and either produce one massive MIF of all of your NTFs together, or one MIF for each NTF. I have read that you should select ‘Separate Tiles’, but this method produces poor MIFs for me just as frequently as the ‘Merge Tiles’ method, so it’s up to you. Press translate and wait for it to finish.
Now, the good news is that if you use MapInfo MIF files are easy for you, and you can go straight ahead and import them. I can’t seem to do that in ArcMap 10.1, so we have a few more steps to follow.
Download and install QGIS. Yes, this is the free open-source mapping software. It’s actually very handy to have around as well as ArcMap, because sometimes it does things much more simply and intuitively than ArcMap and, importantly for us, it can save MIF files as SHP files! You can use it as a lovely GUI for a number of python functions that honestly, I don’t have time to learn how to use. Here I’m using QGIS 1.8.0-Lisboa here.
Using ‘Add vector layer’ button (on the tool bar and featuring a layer with lines on and a + sign), add the MIF files. Now, NTF2MIF produces some text.mif files as well, which I assume contain the numbers associated with the contour line height markings. QGIS doesn’t seem to want to load these, so I’ve done without them: not ideal, but I don’t see any other solutions at this stage. However, you will have the contour lines at least. At this point, you need to right-hand click on each MIF file in the layers screen, and select ‘Save As’. Select the format you want (ESRI Shapefile), etc etc. Now, sometimes this works perfectly and sometimes you get error messages about not being able to save points. In the later case, the contours still seem to save just fine.
If you you’ve only got one SHP file, for instance if you merged your NTFs to a single MIF, you’re basically done. If not, you may want to go to Vector -> Data Management Tools -> Merge shapefiles to one. This is a really simple way of merging shapefiles, but I think they all have to be of the same type (line, poly, point etc), and you’ll need to select the right type in the dialogue. If you’ve ended up with fifty MIF files, turned them into fifty SHP files, you may want to merge them into just one SHP file this way.
If anyone has a better work around for NTF files, please do let me know. In particular, if you know how to get the contour height numbers into QGIS as well, I’d love to hear from you!