1.1 Project Selection
 

Project selection is always the most difficult part of any project, since it shapes the quality of work that will be produced.  This is especially true of GIS projects, which is due to the endless hours of sitting in front of a computer trying different techniques to produce the end result.   If a poor topic is selected the student will become frustrated or bored and not create a project that reflects their abilities.  With this in mind I wanted to select a topic that was of particular interest, which brought me to my family's property near 70 Mile House, British Columbia.

In 1995, my Mom (Liz) purchased 160 acres in a remote location, the property has no roads, buildings or utilities.  Therefore the question of where to put the cabin has been a dinner discussion topic for several years.  There has been two major problems in determining where to put the cabin;

1. The size of the property.  The cabin could go just about anywhere!
2. The lack of time to explore the property.  To date no one has had more than a few days each year to go and check things out.  Therefore, we have only been able to explore areas with the easiest access, which may not be the best place to put the cabin.

The final reason for selecting this topic is that by selecting a good location now, the family will be able to enjoy the property fully.  We will spend more time there!

1.2 The Spatial Question
 

Where to put the family cabin????

The purpose of the project is to reduce the millions of possible cabin locations to a selected few, or at least remove the unacceptable locations from the list.  A discussion with Liz developed the following criteria.

What are all of the locations which;

• have suitable ground for building a structure on.
• are at least 140 meters from the Sandhill Cranes nesting area.
• have a slope of less than 25 percent, since anything greater than 25 percent will increase the building costs.
• are at least 140 meters from the water, so that the septic system will not contaminate the lake on the property.

have sufficient wood value to cover the building cost.  Clearing the cabin location of tree will hopefully provide the revenue to build the cabin.

At this point, it is necessary to discuss data accuracy to ensure that there is an understanding of the limitations of this project.  There is an expectation that when GIS is utilized that the results will be spatially accurate, or in plan english, the output will in fact be a good place to build a cabin.  The problem is not the ability of the GIS software to produce an accurate outcome, but the accuracy of the base data (input).  The old saying 'Garbage IN Garbage OUT' is especially true with GIS.

 Take for example two base data scales, 1:20,000 and 1:100:000.  If we work in metric, which this project does, it is acceptable to expect the 1:20,000 scale to be accurate to plus/minus 20 meters.  Therefore the results of cabin location will be within a circle which has a radius of plus/minus 20 meters.  This level of accuracy could be considered acceptable for this project.  However in the case of the 1:100,000 scale, the acceptable error or accuracy of the data would be plus/minus 100 meters.  This error may not be acceptable for determining the location of the cabin.

It is desirable to select data with an error which is small enough to have little affect on the result of the analysis.  For this project data with a base scale of 1:20,000 would be the most desirable, however data at this accuracy was not always available.  Therefore, it is important to understand that this project is an initial cabin selection.  There is no expectation that the results of this project will identify the exact location of where the cabin will be built.  The purpose of the project is to eliminate all sites which are not acceptable, therefore providing a small number of potential sites.  Liz will need to investigate each location to determine the best location for the cabin!
 

With the level of accuracy desired for the project the following two data sources were dismissed.

• Geological Data from the Land Survey of Canada Web page.  This data set provided the ground composition, which would have been useful in determining acceptable sites for the septic system.  There are strict regulations as to what type of ground composition a sewage lagoon can be built on.  It would have been helpful in the cabin selection process to remove all areas which did not meet the regulations for building a sewage lagoon.


The problem with the data set was the level of accuracy.  The acceptable accuracy of the data was plus/minus 3000 meters, which far exceeded the project expectation.  Therefore, the data set was not included in the project.
 
 

• Watershed Atlas of British Columbia.  This data set has a base scale of 1:50,000 which would could have been acceptable.  However, this data set provides the location of water bodies, including rivers, lakes, ponds, wetlands and oceans.  I was able to obtain a map at a scale of 1:20,000, which included the outline of the lake on the property.  Since the accuracy of the map would be greater than the Watershed Atlas data, this data set was also not included in the project.

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