There are a number of sources that should be investigated to obtain digital information on a site that can be used for creating the base map and base sheet. Some local governmental offices, such as the auditor’s office, tax agency, zoning office, and planning department, have property records including maps in a digital format. Much of this data can be easily accessed online and sometimes can be purchased on a CD and then downloaded directly onto an office computer. Similarly, most surveyors retain their property surveys in a digital format that can be purchased as a CAD file or hardcopy.
A common form of the digital information available online from the various government sources is a Geographic Information System (GIS) database that can be viewed at any scale from the region to the individual property (Figure 6—14). The most detailed scale typically shows the configuration and length of property lines along with the location of the house and other structures on the site (Figure 6—15).
Some GIS systems allow the viewer to add or subtract various site features such as contour lines, flood plains, and utilities as well as view the site as an aerial photo.
If the digital information is obtained as a CAD file or GIS database on a CD, then it can be easily printed at a desired scale. If the information is obtained online, it will likely have to be printed at the size of the screen image and then enlarged via a copy machine to a common graphic scale such as 1" = 10′. This typically requires some trial and error to make sure the written dimensions of the property lines match the scaled distances of the enlargement. Although this technique lacks the precision of a survey, it is nevertheless a viable substitute if no survey exists. The graphic plan that results from this process is good for recording dimensions taken during on-site measuring and as a drawing for noting observations of the site inventory.
Taking and recording measurements directly on the site is the last and most detailed source of dimensional information. The amount and detail of on-site measuring that is required depends on what previous site data has been obtained. If a site survey and/or digital information are available, then on-site measuring serves the purpose of supplementing and adding to the information already obtained. In this situation, onsite measurements might be necessary to locate the doors and windows of the house, paved areas, fences/walls, utilities, plant materials, and so on.
If no site survey exists and/or digital information is unavailable, then on-site measuring is required to locate everything on a site including the property lines, house location, other structures, and relevant site elements. This can be a time-consuming undertaking that requires a high degree of accuracy and organization, as discussed in the following sections.