Edward Turk

Class assignment · Introduction to GIS · ArcGIS Pro

Digitizing green space for a stormwater project

The layers the planners needed didn't exist, so the exercise was to draw them.

What it was

A campus stormwater scenario. Underground detention tanks going in beneath a university mall, and a planning team that needs to know how much permeable surface is up there and where the trees are. None of that existed as data. The aerial is the Carnegie Mellon University main quad, which is the site the exercise uses. The course is USF's.

How it worked

I digitized straight off the aerial imagery in ArcGIS Pro. Green spaces became polygons, walkways became lines, individual trees became points, all drawn by hand at a working scale close enough to see where the grass actually stops. ArcGIS then calculated the area of each polygon and I labeled every one with its own figure. Drawn December 2024.

What I learned

It's a small exercise. It's also the genuinely manual part of GIS, deciding where a lawn ends and staying consistent about that across a dozen features. The first polygon is easy. The tenth one is where you find out whether the rule you started with was actually a rule.

Figure

Aerial imagery of the Carnegie Mellon University main quad with hand-digitized layers drawn over it: pale green polygons for lawns and green spaces, each labeled with its calculated area, thin white outlines for walkways, and bright green dots for individual trees. A legend, north arrow and metric scale bar sit at the lower left.
Green space, walkways and trees digitized from imagery for a campus stormwater runoff project, with each green-space polygon labeled by calculated area. Drawn December 2024.