Projections Part 2: Half the battle

The thing I’ve learned about doing online classes is that traveling and keeping up with the work are not easy. I’ve spent the last 2 weeks travelling between Asia and North America. Between the 15 hour flights, jet leg and new hotels, there is a general screwing with my schedule. Also, Starbucks is my new favorite place since it offers free Wi-Fi, like everywhere (though one must pay 3 bucks for a coffee which offsets the free-ness of said Wi-Fi). That being said, I will say learning projections has been interesting. Now, a lot of this material was covered in my concurrent cartography class but working with it in Arc was good. Though, I slowly, painfully learned the difference between defining and reprojecting. If I’m not mistaken, it seems vector data is the data to reproject because it has already been defined. The raster data I had to define. Once I figured out how to ensure to project my data cleanly, it was like solving a nice little puzzle. Now that I’m familiar with it, I realize how important this will be for my future work in GIS.

In creating the final map product, I decided to go with Pensacola. I figured working with an urban area would be easier for some irrational reason. I found Pensacola by going to the quad search and searching by city name. I then randomly picked a number for the numbers listed under Pensacola, 5259. Using that, I put it in the map. Initially, I was having problems putting in the county boundaries, the x/y coordinates from the excel spreadsheet and the major roads.  So, I went back in the instructions and carefully went through each step using the data I wanted to use. The first time I went through the pdf was on my flight, with a women placing her feet on my arm rest and the man next me taking up my leg area with his legs (there is no personal space in China… L ). This time, I got it right. The processing projecting raster data (othrophotos, .tiff) is different from vector data. With the raster I used the define projection tool and with the vector data, I reprojected the data using the project tool (data management).  A lot of my trouble shooting in ensuring the projections matched up, was opening and closing ArcGIS. I noticed, when you first open an Arc map there is no projection for the data frame. The projection then comes from the first layer added. If you remove that layer and add a new layer with a different projection, there is a conflict that is created because the data frame is using the projection from the first dataset. When defining projections or reprojecting, I had to make sure the GCS lined up. The way I did this was by double clicking the XY coordinate system in the Spatial Reference Properties, this opens a new dialogue, the Projected Coordinate System Properties. Here, you can change the GCS by selecting change and picking a new one. I didn’t do the transformation when the conflicts were first detected when adding the layers. I did it initially, but I found I had a lot of errors. I used the projection tools. Here, I felt I had more control over the projections. 

My take away for the past 2 weeks….don’t travel mid semester and second, projections make all the difference. If anything, knowing projections is half battle in GIS. 

The map displays the required data in the correct projection for this week. If you look close enough you can the edges of the .tiff file behind the aerials. The hardest part was the excel file. This, I had the hardest time with. You really need to ensure the data is clean and correctly converted in the spreadsheet or it won't project correctly, regardless of how you define/project with the Arc Tools.