Coordinate Systems and Spatial Data Models

How to fix misaligned and improperly referenced spatial data:

To align your layers, you first have to check your coordinate/projected coordinate systems through ArcCatalogue. By right clicking>properties, you can view the current system and make changes to match other layers. If this step is ignored, layers will not line up or look true to its actual extent. The purpose of your map will likely dictate what coordinate/projected system you need. If it is a small-scale map, like Vancouver, then UTM is your best bet. If it is Canada being mapped, then the projected system Albers Conic would be ideal. Another option would be visiting the “project” tool in the toolbox. This will change the projection used throughout all layers. Right clicking our data frame>properties will also give you the option of applying the same system across all layers. To avoid having to project on the fly, you would use the “transform” tool to modify data and create a new version of the layer with a different coordinate system. Properties to consider during this process are distance, shape, area and direction – you must decide what properties are needed to be preserved in order to display your data effectively.

 

Landsat Data:

This method of data visualization allows you to avoid common problems with using raster and vector data like the mixed pixel problem. Instead of increasing resolution in your layer, using Landsat data would fix the problem of generalizing data since every point has a value predetermined by radar signals. Although there are restrictions for Landsat data, like how the sun plays a large role in retrieving it, using this energy-induced method of data visualization is still beneficial if you are looking to monitor something over time. In lab 2, we analyzed landsat data of Mt. St. Helen’s before and after the volcano had eruption. New lakes had formed which were picked up with landsat radars, allowing us to view landuse changes as a result of the natural disaster.

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