How to automatically collect data for Geographical Information Systems (GIS)
The term Geographical Information System was coined by Roger Tomlinson in the 1960s. He realised that computers could be used to map and analyse the vast quantities of data that were then being collected by the Canada Land Inventory. However, it wasn't until the 1990s with advances in personal computers that GIS became more widely available to individual scientists, engineers and planners. During this decade article started to be published in technical magazines highlighting applications for GIS. For example, for mobile test and measurement, search and recovery of lost objects on the seafloor, habitat delineation and soil fertility mapping.
The diverse applications all have in common the fundamental properties of a GIS: a computer running software capable of assembling, storing and displaying data identified according to its location. In fact, a GIS is a special case of a data acquisition system.
Collecting Attribute and Spatial Data
Like many data acquisition systems, a GIS needs to assimilate data from many different sources, store and analyse the data. A GIS, though, always references "attribute" data (such as temperature, fluorescence or biodiversity) to "spatial" data (such as latitude and longitude). Sources of spatial data include digitised charts and co-ordinates automatically collected from GPS receivers. Sources of attribute data include sensors and instruments connected to a PC as in other data acquisition applications. Alternatively, some attribute data - such as information from videos - may need to be entered into the system by hand. In all cases attribute data needs to be linked to the spatial data. When data is collected from GPS receivers and PC-linked instruments, this is automatically achieved as all data can be logged to the same date- and time-stamped file. Video evidence, for example, can be later added to the file using the time as a reference.
Decision Making Tool
The prime objective of a GIS is to be a decision-making tool. A useful, and often essential, aid to planning and condition assessment. It uniquely links different sets of data. The data can be presented as tables, graphs, maps or 3-dimensional images. Of course, careful planning is required before implementing a GIS. Not just of what data needs to be collected and how it should be analysed, but of how close together the samples need to be taken. For mobile applications in boats, trains, vehicles, etc, where readings are automatically logged, this translates to sampling speed. Too slow and precision diminishes, too fast and excess data needlessly occupy valuable storage space.
Low Cost GIS
For a simple, low-cost, GIS application you need:
- PC
- Software like Windmill to simultaneously collect spatial and attribute data and pass these to Windows mapping and analysis software
- GPS and other instruments or sensors to collect spatial and attribute data
- Mapping or analysis software
To use Windmill to collect spatial or attribute data, you must make sure you obtain the correct type of driver for your instrument. For example, to acquire data from instruments with RS232 ports (such as GPS receivers, echo sounders and many other lab instruments) you need Windmill with the COMIML serial driver Windmill can also handle GPIB, Ethernet, USB, RS485, RS422, Modbus and ISA-bus devices.
This article has was originally published in Monitor (ISSN 1472-0221). To subscribe to Monitor please fill in your email address below. We will not pass your address to any third parties.
