data and digital imagery (Mapping 
Science Committee, 1994) are 
considered to be fundamental for GIS 
usage, especially at the national level. 
In the above report, the Mapping 
Science Committee (MSC) has 
identified five other important data 
sets: 
1.) The digital orthophoto 
2.) A street centerline file 
3.) A cadastral framework 
4.) A natural resource 
framework 
5.) A hydrological framework 
A recent user survey by the Ohio 
Geographically Referenced 
Information Program (OGRIP) 
confirms these selections at the “local” 
level (Ohio Geographically Referenced 
Information Program, 1993). In this 
survey the following data elements 
were considered to be of the greatest 
interest: 
1.) Geodetic control 
2.) Parcel attributes 
3.) Right-of-Ways 
4.) Bridges 
5.) Parcel boundaries 
6.) Street attributes 
7.) Street centerline 
8.) Municipal boundaries 
At first glance, the difference between 
national needs and the local needs 
appears to be in the natural resource 
area, however, the OGRIP survey 
found that the top five data sets that 
needed to be entered into the 
respondents databases were: 
156 
1.) Flood plain 
2.) Watersheds 
3.) FEMA zones 
4.) Land use 
5.) Zoning 
It is important to note that the 
combination of "most interest" and 
"most needed" data by the OGRIP 
survey, corresponds to the more 
national findings of the mapping 
science committee. 
ACCURACY CONSIDERATIONS 
The OGRIP survey was weak 
concerning accuracy requirements 
however according to that survey, 
almost all "GIS" accuracy requirements 
were satisfied by s = +2.5 feet. It is 
pointed out by the MSC that one man’s 
"accurate" is another "inaccurate" 
depending on the application. The 
following table illustrates that fact. In 
any event and contrary, | might add, to 
recent emphasis by the National 
Geodetic Survey, most applications of 
spatial data leading to decisions 
relating to land development, 
environmental problems and even 
utility line siting, are satisfied by 
accuracies of s = ¥0.1m. This 
assertion differentiates between 
surveying and GIS usage. However, it 
should be pointed out that in a recent 
article (Fernandez-Falcon, E., et. al., 
1993.) a suggestion is made that 
spatial accuracy needs for surveying 
may actually be declining, except for 
geodynamics, because error 
propagation resulting from GPS 
surveys is completely different from 
that encountered by traditional 
techniques, and the cost per point has 
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