Following the previous post where I pointed to a few sources of map data, I thought I’d write about importing them into ArcMap 10.1, particularly because it’s been quite labour intensive and whilst there are plenty of walk-throughs on the respective websites, very few of them have solved all my problems. I should say I am really not a GIS expert. I’m just sharing some methods that worked for me, as a novice, and they are likely to be quick and dirty and potentially not the best method.
So first up are the many layers of data available from Edina DigiMap. This data is only available through an Institution, and even then they make you sign up individually and wait to get your ‘approval’. And the service logs you out automatically after 30 minutes.
It’s worth saying that when you order your DigiMap, keep the text files that come with the data files, preferably all together. These contain important metadata, and they also record the licensing conditions which you need to know for publishing your maps, etc.
Boundary data vector files (shp)
So first things first, you need an outline of the UK, or your county, or individual region (England, Wales, Scotland). You’ll need to go to the Ordnance Survey tab, click on the ‘Download OS mapping data’, and then select ‘Boundary Download’. Hey presto, ‘GB National Boundaries’ data is available at the bottom.
As I’m using ArcMap, I’m going to select ‘shp’ files where possible, because they are the software’s favourite format so a damn site easier to work with as a novice than anything else. Follow through all the screens to process your ‘order’, and download the data.
Getting the data into ArcMap
This one is easy, really. We’ve got shp files so all you need to do in ArcMap is click the Add Data button, which is a little yellow diamond with a black + sign in it. Voila!
OS Mastermap Topography raster files (TIFF)
This is the most detailed mapping layer for Britain, as 1:1000. It is almost too detailed and rather colourful, but you might want it as a base layer for mapping trenches etc on top of – it really is that detailed. It comes as TIFF files, which are image files, along with lots of other files which will tell ArcMap how to relate the TIFFs to each other.
Getting the data into ArcMap
If you only have one TIFF file, just add it like a normal piece of data. However if you’ve got lots of them, I found the method below produced the smoothest results from all the ones I tried.
Open up ArcCatalog in ArcMap. This might be a ‘Catalog’ button on the right hand of the ArcMap screen, or there’s a little symbol button for Catalog on the main toolbar. The Catalog appears to be a file management bolt-on system, amongst other things. Navigate to the place you’re using to store your GIS files. Right-hand click the folder, and go to New -> File Geodatabase and give it a name, etc. Right hand click your new geodatabase and make it your default geodatabase.
Within this geodatabase we’re going to create a mosaic dataset. Basically we want all the image files of our map in one layer, lying next to each other in the right positions, so we want a mosaic. Right-hand click on your new Geodatabase and go New -> Mosaic Dataset. Go through the dialogues and select your options; in particular you want to make sure the Spatial References are right (ie, if you’re using British National Grid you need to select this). Make sure you name it correctly first time, it seems reluctant to change names once created.
To fill this empty mosaic dataset with files, right-hand click on it, and click Add Rasters. Make sure the Raster Type is set to Raster Database, and use the Input Data type, Dataset. In the advanced options you can specify the coordinate system, and when you’ve finished you can click OK and wait for the programme to process the command. It will take some time.
The new mosaic dataset should appear automatically in your map window; you may need to zoom in, or right-click the layer in your list of layers and select ‘zoom to layer’. If it hasn’t been added, you can drag it in from the catalog interface.
OS Mastermap Topography Vector files (GML)
Integrated Transport Network and individual topography selections at 1:2500 are produced as GML files.These are the kind of poly and line shapes you’re used to seeing and might be the best for mapping detailed stuff on top.
When you download these you get contents text files and it is important these are kept with the original files and folders. The download comes with a PDF file on how to get these into mapping software. If you have the Productivity Suite extension for ArcMap, you can follow the instructions listed there. If like me, you don’t, then you’re limited. The guide says ArcMap can open GML by just clicking the ‘add data’ button, but that doesn’t work for me at all. So that leaves one option: converting the files using InterOSpe.
Download and install InterOSpe, and start up the Processing programme, which needs you to tell it where the contents text file is so that it can read through that. You don’t need to unzip the GML folders, so leave them be. After that it’s pretty straight forwards, just click through the numerous dialogues and set the programme going. What you should end up with is lots of shp files, which you can add as usual. You end up with some which are lines and points for placing the gazetteer text; the easiest solution to this problem I’ve found so far is to right-click the ‘gazetteer’ layer (once you’ve added it), go to properties, remove the points entirely and use the ‘label’ feature to call the INDEX_NAME field and write that as a label.
There’s a crazy amount of work in turning all the different line types into the right colours, but that can all be done. InterOSpe is supposed to come with the right symbology for OSmaps, but the output still seems to need a lot of work.
Historic County Series raster files (TIFF)
There are a lot of historic maps, but as I’m looking at a rural location I’m not using the Town Plans. In the County Series there are 1:2500 and 1:10560 schemes, and you can have the original sheets, the national grid tiles or both. These are great for looking at changes in landscape, doing a map regression, or in my case for looking at the landscape of your site before the water board put a reservoir over half of it!
These are delivered as TIFF raster files, so you can follow the method discussed above under OS Mastermap Topography.
That’s it for now… there’ll probably be other posts later when I tackle some of the other file types, and possibly some discussions of the Roman datasets, though they are remarkably more easy to import (thank you, digital classicists!).
Ruth Fillery-Travis 