Saturday, April 11, 2015

Georeferencing, Editing and ArcScene

This lab exercise was more challenging in some ways but certainly more fun than others.  We took on the task of Georeferencing, Editing and learning more about ArcScene.

Georeferencing is a process to tell a raster dataset (in our case two raster datasets- aerial photographs- of the UWF Campus) where they belong in space-- giving the aerial images a spatial reference.  The steps to do this are pretty straight forward though there are a few items to emphasize here:

1. When you create a Link, always click on the unknown raster image first, then click on the known or referenced data.
2. You must consider the overall image, not just the RMS (root mean square) of the map;
Having the lowest possible RMS and highest order polynomial is not always best-- at higher ordinals, the image may bend and distort.
3.  Zooming to a link point on a raster image is an art: I learned that you can zoom too close and the image just blurs and makes it impossible to accurately find the corner you were looking for. Therefore, knowing what "looks right" is an art.

As for the Editing portion of this Lab, I learned we can create and edit several kinds of data.  This includes points, lines, polygons, and text. We experimented with editing a UWF road (line) and a building (polygon),that represented the new gymnasium on UWF. In this lab we digitized this data on the UWF Campus. One important lesson with Editing is to Save your work.  I think saving your work is always important, but in Editing for ArcMap, your edits are not automatically saved and you would lose your data (edits) even if you saved your map and closed it. This almost happened to me, but it was a great learning opportunity.

ArcGIS Resources has some great information about Editing. I particularly enjoyed:
Fundamentals of Georeferencing a Raster Dataset: Should you rectify your raster? 
A good read with loads of useful information. Below is a look at my first map:

Finally, ArcScene was a blast! The most challenging part was using the Navigate function:

Navigate: This is the standard navigation tool. Click and hold the left mouse button to rotate the view, click and hold the mouse wheel to pan, and spin the mouse wheel to zoom in or out.

Sounds simple, right? I thought so too, but it was quite a challenge. My computer lagged and I never seemed to get to the view or the point I was aiming for.  Guess I need a new computer....wait...I did buy a new computer a couple of days ago. My first new computer since...well, I won't's really been a long time.

Anyway, back to ArcScene;
Using the UWF_DEM (digital elevation model) to add texture and depth to my map was excellent. I very much enjoyed using the Extrusion capability and then adding a Vertical Exaggeration to really pump up the 3D effects. Below is the image of my ArcScene before I added the essential map elements:
So, overall this lab was quite informative albeit, frustrating due to the slow connection and my outdated PC. However, now I have a new, faster PC,,,so no excuses...Let's Make A Map! Below is my final ArcScene Map.

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