Creating Your Base Map
A base map is a spatial representation of your property as it is at the present time, before you begin the process of site analysis and before you do any new site development. It should include property boundaries, drawn to scale, and oriented with respect to compass directions. Your base map should indicate major landforms including hills, valleys, ravines, wetlands, forest edges, streams, etc. It will also include the location of roads, bridges, buildings, utility rights of way and any other fixed features, natural or man made. An example baseline map may be found at the end of this section. [The MNG Case Study Workbook provides another example ].
The best starting point for a base map is the survey map associated with the legal deed to the property. In most cases boundaries, directional (compass) orientation, angles, etc. are accurately represented based on a professional survey. It may be advisable to walk your property lines to make sure your understanding of the boundaries corresponds to the survey map. The adjacent property owner should be in agreement, so there is no confusion or disagreement about the location of posted signs, fences, etc. Drawing on or otherwise altering your survey map is not recommended, so make several copies or tracings (at least 3) of the survey map. Use one for your base map, one for your site assessment map, and another for your design map. Be sure that your map includes a scale indicator such as “1 inch = 500 ft”. It should also include a directional indicator, such that N at the tip of an arrow points North relative to features on your map.
Mapping from Scratch
If no survey map is available, then it will be necessary to create your base map from scratch by walking your property lines and carefully measuring distances and directions with a compass. If a high level of accuracy is not critical then you can estimate distances by counting your paces and multiplying the number of paces by the average length of your pace. More specific guidelines for creating a base map may be found in the Toolbox below, Base Mapping Resources.
Adding Features to Your Base Map
Topographic maps and aerial photographs are useful resources for adding landform and elevation data to your base map. We discuss each in turn.
A “topo” map, or “quad sheet” usually refers to a 7.5 minute (1:24,000) USGS topographic map. These maps exist for the entire USA. The USGS topographic map section corresponds to your site so you can “see” hills and valleys in relation to each other, and other topographic features such as lakes, streams, marshes, roadways, etc.
Topographic maps can be obtained from a variety of sources including outdoor-activities equipment stores, public libraries, or ordered online directly from the US government’s USGS web site, which is provided in the Topographic Map Resource Box below. Each map has a unique name which can be used for ordering it. The USGS “Map Locator” online resource, also described in the Resource Box, can be used to determine which map corresponds to your area.
There are also numerous commercial websites that will custom assemble a topographic map from any area you specify, and you download (for a fee) a digital copy of that map. This could include only part of one or parts of several official USGS maps. USGS Topographic maps are also available at some public libraries. It is important to remember that USGS topographic maps are at a much larger scale (1”= 50,000) than a typical property deed survey map (1 inch = ?). Interpretation of map symbols and other information about using a topographic map are explained by Jim Ochterski in Using Topographic Maps in the toolkit below.
If you are able to acquire aerial photographs of your site, they can be useful for estimating forest cover density and other visual features such as the location of buildings. According to Jim Ochterski, “Aerial photographs will help you get a bird’s eye view of your forest. With it, you will see features you’ve not seen before.” One option is to draw your property boundaries and other features directly on to a sufficiently high resolution aerial photograph of your site and use it as your base map. Aerial photos can be obtained from a number of commercial online or other sources. Several sources are listed on the USGS website, View Online USGS Maps and Aerial Photo Images.
Now that you have some understanding of the types of maps available that may be useful to you, notice that [ Workbook page 4 ] provides an opportunity to record those you wish to reference and from what sources you obtain the specific maps. [ See the MNG Case Study Workbook ].
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