Five steps to simple GIS application

Now that total Global Positioning Systems (GPS) packages, with hardware, software and receivers, are more affordable, city and county officials are considering GPS equipment purchases for a variety of municipal applications, especially when implementing GIS surveys.

But even with the widespread availability of GIS tools, many cities and counties still plan their GPS survey projects using time-consuming, manual methods. In some cases, the latest technology is not available to the municipalities and budgetary constraints are limited.

Yet, at times, two weeks or more are required to review information manually on lengthy, hard-copy control reports to determine acceptable control for a project. Control points must then be plotted, usually on quad maps, before survey points can be chosen, a task that leaves the project open to error.

However, using the new GIS tools, surveyors can save time in the planning stage and prevent costly errors. GIS tools can reduce GPS project planning time by 25 percent to 50 percent.

All the city or county needs is a PC, desktop GIS software, a commodity base map and a conversion program.

The five steps for GIS application are:

1. Acquisition of the hardware, software and data for creating the digital database. Requirements include Windows-based GIS software with database capabilities, a commodity base map of the project, digital National Geodetic Survey (NGS) data, a laptop PC and an optional plotter;

2. Use of the GIS software, with the initial hardware purchased, to access the commodity base map. Data layers are selected and the project area reviewed to determine the locations of road and water features as well as potential obstacles for GPS surveyors;

3. Conversion of the NGS data set after the software is installed and reviewed. A programmer familiar with the GIS database software can write a computer program that extracts specific data from the digital NGS data sheets, such as “horizontal order,” “station mark” and “point ID” and place it into a GIS database table. This program, which converts the detailed digital inventory of NGS control data into relational database files, allows Standard Query Language (SQL) queries to be performed later;

4. Creation of a graphic point in GIS for each NGS registered control point in the project area once the files are converted. This task is completed using GIS software. Afterward, all NGS control points are available as displayed graphic objects on the GIS map; and

5. Analysis of existing control data to determine what points exist and, if new survey points are being established, where they should be placed.

By performing SQL queries on the database, users can choose, display and colorcode needed control, such as all first-order horizontal points, all second-order horizontal points, and so on. Additional colorcoding and symbolizing can then be completed to give the surveyor critical data about each point.

Using manual methods alone, this step requires about a week. Using GIS tools, it is possible to analyze control data and prepare session maps for an entire 600-squaremile county in a single hour.

The survey information for GPS sessions is available at a glance on the GIS map, instead of being buried in hundreds of paper data sheets. These maps which are more accesible, can be plotted to produce a project layout for GPS field crews.

When municipalities adapt GPS tools in GIS reporting, information is streamlined and more accurate, data collection time is lessened, and city and county costs are reduced by decreasing survey crew work hours during GIS reporting.