Wednesday, 21 April 2021

Tree planting survey - Part II

[ In the news: ‘Amazing success’ as community group plants 165 trees by banks of river Cam ]

The previous Tree planting survey 1-2-3 showed what3words used to located and post on a web map rough surveyed locations for tree planting directed by a tree surgeon, to help restore tree rows along the River Cam towpath immediately north of Cambridge UK. The beauty of turning out a web map the same day as the survey, is that shortly after, printing out the same map for tree-planting volunteers to take into the field was feasible almost as quickly. So after a 'high tech' Part I, here's a 'low tech' Part II.

This was inspired by a previous effort to demand Cambridge University Colleges divest from fossil fuel investment, by pointing out how far each college would be under water if sea level rise occurred as a result of unabated climate change driven by fossil fuel industries. Maps4campaigns resulted in a simple A4 sheet posting College locations, their potential submergence and their divestment status.

click ot enlarge

The requirement is for volunteers to take a sheet of paper, in a plastic sleeve against inclement weather, they can refer to but most importantly fold into their hip pocket when they start digging holes to put sapling and whips in. While I used what3words app on my smartphone, there's no way we could train dozens of volunteers to use that app, when tree locations are all they really need. what3words was used not only for its ease-of-use but also the the 3-meter-square precision was amply sufficient ot spot tree locations. 

The simplest then is to convert the web app - used to post tree spots for the sponsors to approve the project - into maps sheets as directly as possible with no transcription error. So the same way we used what3words locator for ArcGIS Online, let's used waht3words locator for ArcGIS Desktop to post the same on desktop instead of mobile or web app. 

But simply posting A4 sheets following the Cam towpath required a few decisions:

  • what scale? 1:1,000 put enough of the river section to spot locations against an OpenStreetMap background to give identifying clues for planned tree spots (below right)
  • 1:10,000 post the surveyed river section on an A4 sheet, and can serve as an index map to show where the detailed maps are located (below left)
  • then a simple grid markup akin to atlases is used to identify and classify the large scale maps

click to enlarge

Voilà! A dozen A4 sheets plus and index cover the survey area, and can be copied and distributed among volunteers in the field - that's the low tech meeting requirements of ease-of-use in the field. But that resulted from prior recording location on a smartphone in the field, exporting CSV files and posting both web and desktop maps with no intervening manipulations or sources of error - that's the high tech meeting requirements of a surveyor minimizing errors in data capture and manipulation. Moreover, the what3words app had these advantages: enter freehand text to record the tree surgeon's counts and descriptions, and then correct the few GPS wobbles where the smartphone mis-posted a location.

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