Mobile GIS & LBS
Matt holds an MSc in Geography and GIS. He has been working with clients solving problems with GIS for over 17 years. Matt founded WebMapSolutions whose mission is to put innovative, intuitive GIS driven applications into the hands of new and existing users.
Offline Mobile Map Basics: Editing Map Layers Offline
September 5th, 2016 by Matt Sheehan
In our second article in this series: Offline Mobile Map Basics: Offline Base-Maps and Layers, we discussed how to take base-maps and layers offline. From Esri-land Tile Packages (TPK) and Feature Layers were key discussion areas. In this third post in the series we will dig a little deeper and focus on offline mobile map editing.
Editing Map Layers Offline
As we have discussed in the previous two posts, base-maps are static. That means they are simply images or tiles stitched together to provide context. Layers are what sit on-top of base-maps and if the are Feature Layers they can be edited. What do we mean by edited? There are three types of editing:
1. Add – Imagine you are working in the pipeline industry, and are viewing on your iPad the current pipe network in an ArcGIS map app. You are currently extending the pipeline; adding an additional line. You will need to update the pipeline layer to include this new section of pipe. That means adding a new line feature.
2. Edit – You are out inspecting a power pole. When you tap the point feature which represents the pole in you mobile map app a list of attributes appears, these describe the pole; type, last inspection date etc. You notice the pole is listed as metal when you can see it is actually wood. You need to edit this features ‘material type’ attribute so it is accurate.
3. Delete – You are a member of a team who are demolishing a power station. Once complete you will need to update the power station map layer and delete this feature.
These are the three fundamental edit options with a map layer. Often those needing to make edits to a layer are in the field without a wireless connection. So how does offline map layer editing work?
In the same way that base-maps and map layers are stored on you tablet or smartphone for offline viewing, edits need to be stored locally. That means any add, edit or deletes are stored in a database on your mobile device. Should your mobile device lose power or the mobile app crash, the edit data is not lost since it is written to a permanent storage area. Now these layer edits are not much use stored only on your tablet or smartphone. When back in the office, the edit data needs to be written back to the layer source. In Esri-land that means written back to the ArcGIS source layer. A button in the mobile map app is often in place to push these edits to the layer source.
There is one more edit option which needs mention. Adding an image of the feature is often important. A record of the ‘current state’ of a feature, for example, can be very useful. These are called attachments. An attachment button, which is often part of the editing pop up window, opens the camera on your tablet or smartphone and enables you to take and attach a picture to the map feature. Again in offline mode this image is linked to the feature and when back online the feature image is uploaded to the layer source with any other edits.
That’s it for part 3 in this series. In our next article: Offline Mobile Map Basics: What are your Choices, we will pull everything together and discuss your options for working with mobile maps offline. See you next time.
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