Your GPS needs to be able to “see” at least four satellites. Trees or tall buildings can block your GPS’s line of sight, and GPS isn’t suited for indoor surveying. In such situations, an optical total station may be more cost-effective.

 

Depending on your application, you can choose from several measuring techniques:

 

For long lines, geodetic networks, or tectonic plate studies, use static measuring. It’s extremely accurate over long distances, but slower than other methods.

To establish local control networks, network densification, or related jobs, use rapid static measuring. Also highly accurate for baselines up to 20 kilometers, rapid static is much quicker than static measuring.

 

If you’re doing detail surveys or measuring many points close to each other, kinematic measuring may be your best bet. This depends on whether your instrument can see four satellites in the clear. Otherwise, you’ll need to reinitialize, which can take between 5 and 10 minutes – unless your GPS has on-the-fly processing capabilities.

 

Another technique is real-time kinematic (RTK), which uses a radio data link from the satellites to the reference receiver and on to the rover. This allows for real-time measurements, as long as there’s no radio interference or line-of-sight blockage. RTK is useful for detail surveying, stakeout, and COGO applications.

 

Static measuring is the original GPS surveying technique. To measure a long baseline (20 km/16 mi and up), place the reference receiver at a known point. Next, place a second receiver (called the “rover”) at the other end of the baseline. Then, set identical data recording times – usually 15, 30, or 60 seconds – and measure for at least one hour. Depending on how long the line is, how many satellites are in sight, and their relative geometry, you may need to measure for a longer time. Remember: measure twice to avoid mistakes. Once you collect enough data, turn off the rover, move it to the next baseline, and repeat the process. For even greater speed, add another rover and alternate the two rovers’ placement to measure each line.

GIS is an integrated collection of software and data that visually organizes information around the concepts of geographic location and space. GIS can be used for geographic analysis, map making, database management, and geospatial statistics. GIS can be applied to many applications in several fields of study. You can use GIS to:

 

-Study the distribution of populations
-Study physical features of the earth and natural phenomena
-Find the optimal location for starting a business or locating an event
-Identify markets to target
-Identify geographic patterns like clustering
-Determine the best routes or paths to follow
-Tie together separate pieces of data to create new information
-Create maps

-Geographic features are stored in individual GIS files. These files are the raw materials for geographic analysis and map making
-GIS files are georeferenced, which means features are drawn to scale and

  tied to actual places on the earth via coordinate systems and map projections
-Since coordinate systems and map projections are standardized, GIS data from many sources can be shared
-GIS files come in several different formats; they can represent continuous surfaces (raster) or discrete geometry (vector)
-GIS software is the tool / window for viewing, analysing, and manipulating GIS data
-Data tables that are place-based can be converted into GIS data by either plotting the

 table data using latitude and longitude or by joining table data to GIS features using a common ID code