by cengel on May 23, 2011 at 3:23 pm
Corvallis Microtechnology Inc, an Oregon based company that specializes in survey and mapping soft- and hardware for forestry and related fields, released a free iPad app iCMTGIS last summer, which appears to be a port of their Windows-based and Windows CE-based survey software. This app turns the iPad into a mobile field mapping and data collection device for GIS data, somewhat similar to what ArcPAD does for ESRI. (This is a longer post. If you are in a rush, jump to the bottom ).
Here is the impressive list of features from the company’s website:
Pre-define feature descriptions to facilitate data collection.Display GOOGLE map or load a raster image prepared by PC-GIS for use as the background map.Record the GPS location of Point, Line and Area Features.Traverse a path or an area.Label features with symbols, IDs and descriptions.View Feature locations in LLA, UTM, or SPC coordinate system.View Lengths, Areas & Perimeters.Manually digitize Points, Lines and Areas.Create a grid for your job site to perform sampling tasks.Import/Export data in Shapefile format.
The downside is that at the point of writing, I was not able to find any documentation of how to use the app. There is no help button, the link to the Online Handbook is broken and googling does not take you far.
On the other hand, after spending some time with the app, I was quite impressed by its capabilities. I was able to take the iPad around campus, log locations and tracks and directly import them into a GIS on my desktop. There are a few quirks, but here is how it worked for me.
This is the menu bar for your orientation.
1. The application uses its own terminology, so in order to start collecting data it is necessary to first define a so called “Job”. A job, as far as I understand, is a container that can hold a number of different layers, (in this application the termed “Topics”). Go to the top right icon: Main Menu > Job > Current Job, choose new, which will assign the Job an arbitrary name, replace this name with one or your choice, say OK and Exit.
2. Next step is to define a “Topic”. As mentioned above, a Job can contain several “Topics”. This appears to refer to the data type, raster or vector (ie shapefiles). When recording data the Topic is typically a shapefile, so you will need to define it as point, line or area type. Topics are can eventually be exported as shapefiles (see below). Each topic, of course, creates a different shapefile. Go to the second from left icon: Topic > New Topic. Name it, choose Point, Line or Area as type, say OK, then add attribute fields. To toggle the attribute window of the active Topic on and off at any tome use the menu button on the far right.
If you haven’t done so, go to Main Menu > Google Map > and choose your preferred basemap.
3. To start recording data, toggle on the GPS from the Menu bar at the top GPS > on. Use the same Meny button GPS > Collect. This will popu up a new window. Choose New and as feature name enter the name the name of the “Topic” you defined earlier. That will automatically enter a featuereID. I left all the other options as default. The chosen feature (Topic) will appear in the new window, together with the attribute data fields defined earlier. It indicates standby mode in its status. Click on the eye to toggle the attribute table into editing mode, indicated by a pencil. Enter the attributes of your object, then click Store. The app will take 20 seconds to store the point, indicating “storing” in its status, after which it returns to stand-by. Repeat this for additional points.
4. To record a track, add a “Topic” of type Line. Then go to GPS > Collect. Points will be collected in the chosen interval until to click Store. It appears that points are not stored immediately, but only when the Store button is clicked. Then the points selected up to this point will be stored as one track and collecting of the second track starts. To finish tracking, stop Storing or go to Exit.
To toggle off and on the the different layers (“Topics”) of a “Job” use the button second from the right.
It is possible to add points manually. This may be preferable under certain conditions, particularly if a detailed basemap is available, and the location of an object can be determined visually more exactly. Horizontal position accuracy was for me around 30m the few times I checked, but this may is not representative. Instead of using GPS > Collect, use the third Menu Button TOOLS > Add point manually (for example), enter attribute data (optional) and mark the point on the base map.
To export the data for further use go to MAIN MENU > Shape File > Export. Choose the files you want to export and say OK. Note that there is no message telling you about successful saving. You will only receive a warning when you try to overwrite an already existing file.
Connect the iPad through USB with the laptop use to drag from iCMTGIS to your laptop. Note that you need to copy all the components of the shapefile, which are: .shx, .shp, .prj, and .dbf files.
And finally, below are my recorded data imported into a GIS.
Note, however, that despite storing a unique feature ID, this ID is not transferred with the attribute table. So it is probably a good idea to add an additional field to the attribute table and record your own unique ID.
The application worked perfectly for me, and compared to my experiences with many other apps, appears to be quite stable. It did not ever crash during the recording process, nor did I loose any data. I had an occasional memory low message, which I ignored and which did not appear to have any impact. However, I am not certain how the app would work with large datasets. In addition to maybe memory issues, the transfer of numerous files out of iTunes could be a messy endeavor. Also, there are a number of files that can be seen on the device, that probaby should not be touched, or worse, deleted.
Shapefile import works without a glitch. Raster images can be used either as basemaps or as layers, however, they need to be in a proprietory .pim format, which can onlt be generated by using another commercial software of the company (PC-GIS).
There is an option to use an already existing feature list for data collection, however, I did not try this. One of the things I was not sure about is how to add a new feature list other than duplicating and editing the existing one.
iCMTGIS (Free, iPad only)
Pros: Very stable and reliable, powerful options for data collection, including preset feature lists and attribute data, easy import and export of shapefiles through iTunes drag and drop.
Cons: Currently no documentation or help, import and export of shapefiles clumsy, thus not recommended for huge amounts of data, some non-intuitive interface elements, can deal with raster images import only in proprietary format.