GETTING YOUR GIS PROJECT
READY
In this project you
will be exploring and mapping the historic coal mine activity of
The main GIS
techniques you will need to get your project ready to create some maps are,
1. Georeference the different data layers you want to use
to the same datum and geographic projection and,
2. Clip the data layers to
1. Georeferencing
Open Arc Catalog (start|ArcGis|ArcCataog)
and navigate to your data folder.
Inside there you should see a folder called “Historic_coal_mines”
and another called “Extras”. The first thing you should do is gather
information about the geographic projection (a.k.a. spatial metadata) of the
different data layers. To do this, highlight a data layer on the Catalog main
window and press the metadata tab. Once in the Metadata window, press SPATIAL. There you will see a
description of the spatial coordinates of the shapefile. Make a mental or
written note about the information you see. In the example below I am looking
at the spatial characteristics of the INDEX shapefile. The KEY characteristics
are Horizontal
coordinate System and (under Details) the Horizontal datum name. Explore
the spatial characteristics of all shapefiles in both folders.
After you are done
exploring the spatial metadata of your shapefiles you will notice 2 types of
information. One group of data has a NAD27 UTM ZONE 13N projection defined and
the other group of data does not have any projection defined. It is important
to have all your data layers georeferenced to the same projection so you will
need to fix this issue. In this case however, your data layers do not have
different projections; rather some of them do not have a projection defined.
Defining a projection is a simple process, and it is done using ArcTollbox.
Launch the Toolbox
from ArcCatalog by pressing the little red toolbox button
.
From the toolbox open
Data Management Tools and then open Projections and Transformations (see
below)
To define a projection to a dataset double-click Define Projection.
A dialog box comes
up where you need to specify which layer needs a projection definition and
which projection to use.
In this example I’m
defining a projection for the coal_mines shapefile.
Noticed that the coordinate system says “Unknown” (If it says otherwise, it
means that your layer has already a projection defined).
Next, press the
button to the right of Coordinate System. This will open up the coordinate
systems settings window, where you can choose between two options (remember
that the projection you will use for this project is NAD27 UTM ZONE 13N).
You can manually
set the projection for you data by choosing Select… and navigating the folders until you get to your projection
file.
A simpler method
can be used if you already have a data layer with the projection you are
looking for already defined. This is the case in your project, where the layer INDEX.shp has the NAD27
UTM ZONE 13N projection defined.
For example, you
can assign the projection of the INDEX layer to your CoalMines
layer by choosing Import… and selecting
the INDEX file.
Press Add then OK, and finish the Define Projection dialog box. Repeat these steps
for all the other layers without a projection defined.
1.2 Re-projecting
Another situation
you can encounter is that simply the projections of your data layers do not
match.
This can be the
case if you use others sources of data in your project. To re-project a dataset
the steps are almost exact to the ones you just did for defining a projection.
In the toolbox, under
Data Management Tools/Projections and
Transformations open Feature and select Project.
This will open up
another dialog box where you need to set the new projection to you layer.
You will notice that
the steps are very similar to defining a projection. Be careful about destination folders and file names.
If you encounter an
error saying you did not specified transformation choose a Geographic Transformation
in the dialog box (ask you TA for assistance in choosing a transformation).
After you have
georeferenced ALL your data layers, open Arc Map and load your data. Arrange
the layer so you can easily explore them (polygons below lines, and point,
proper symbology, colors, etc). The first thing you should notice is that your
most of your data is at the state level, and we are only interested in
You will do this by
selecting and exporting relevant data from Arc Map and Clipping other data
layers to fit only
First, using the select
feature pointer 
select
To select the mines
that are inside
First, make sure nothing
is selected in your data. Next go to Selection and choose Select by Location
This will open up a
dialog box where you need to set you selection criteria.
The setting are
shown below, I want to: select features from | the following layers:
(check coal_mines) | that: have their center in
| the features in this layer: (check your
boulder county layer).
Hit Apply.
If things were set
properly you should see only the coal mines in Boulder Co. selected.
Export the selected
data to your BoulderCoal folder.
Another GIS
technique that works nicely in this project is the Clipping function that literally
‘clips’ one layer according to another.
For example, say
you want to create a road layer just for Boulder Co. You can clip the state roads
layer using Boulder Co. as the clipping feature and create the layer you
wanted.
In Arc Map open the
Toolbox and expand the Analysis Tools.
Select Extract and double click on Clip.
This opens up the
Clip dialog box where you tell the program what you want to do.
In this example I’m
clipping the roads layer to fit Boulder Co.
See the image
below.
You can actually
drag the data layers you want to process directly from Arc Map.
Make sure you save your
new shapefiles in the right places and using meaningful file names.
Using the
techniques I showed you in this tutorial you can process and prepare all the
necessary data to complete your project.
Bellow is an
example of a view of south east boulder, where the majority of the coal mines in
the county are located. Urban areas are represented by dark shades. As you can
see, this view is ready to become a real map, by adding scale, locator maps, text,
legend and so on…
It is up to you to
create the maps you need and come up with cartographic designs that suit your
particular point of view about the project. The GIS project is ready. Explore
and have fun.
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