A Level

# Using GIS

## 4. Using GIS

Good fieldwork data collection is well planned. The special feature of GIS is that each piece of data is tied to a particular location. So GIS can help you plan both where you will collect data and how you will collect data. To get the most of out GIS, there are a few technical terms that it is useful to know.

Your data collection will involve a combination of be taking measurements, making observations and recordings - these are the data - in GIS they are referred to as attributes

You will have decided on a sampling strategy for your data collection – for GIS you must record where data comes from as well as the data itself – this is the location.

• What data to collect (what attributes?)
• How to record that data (what attribute types?)
• How to record locations (what location types and location format?)

## How will you record data?

When planning how you will collect data you will know what data you are going to record at each location. In GIS speak these are the attributes, the things that describe the location. Each location can have many different attributes recorded, there can be one or many attributes recorded at each location.

For each attribute GIS needs to know the format of the data you are expecting. There are four broad types, with different names used to describe each.

Example of data type Description of data format GIS calls this
A count of the number of houses within an area.An environmental quality survey score.  A whole number Integer or Short or Long
The length of a pebble on a beach A number with a decimal point
(GIS might allow you to define the number of decimal places)
Float or Double or Decimal or Real
Answers to a question within a questionnaire – “Where have you come from?”
A set of characters of any type in any order – Text or text and numbers String or Text
1st May 1982
30th January 2017, 15:55:54
A date and/or time Date

Choosing the right attribute type is important as the wrong choice can make it harder to map your data correctly in GIS.

### Recording location

GIS represents locations as one of three different location types - either Point, Line or Area (Polygon). Which you use will depend on the features you are describing, and the coarseness of the scale you are working. Your data collection might use a combination of points, lines and polygons.

### Location types

 Point A single location Locations of individual trees Line Several linked points in a known order Route taken through a town for a dérive Polygon Several linked points in a known order to form a closed shape Area of uniform land use or a census output area

As well as deciding what type of location to use, you will need to decide on the most appropriate format to define them.

Sampling locations for pebble measurements have been chosen on map in the classroom, you need to navigate to each sampling point to collect data

 Location Type What location format? Considerations Point Latitude and Longitude or Ordnance Survey grid reference Use GPS app or appropriate map to navigate to location. You will need to convert OS grid references to Lat/Long for most GIS - Convert at doogal.co.uk Batch Reverse Geocoding

Record the location and orientation of striations identified in the field

 Location Type What location format? Considerations Point Latitude and Longitude or Ordnance Survey Grid Reference Use GPS app or appropriate map to identify current location. You will need to convert OS grid references to Lat/Long for most GIS - Convert at doogal.co.uk Batch Reverse Geocoding

Recording and mapping visitor response to “Where have you come from?” question

 Location Type What location format? Considerations Point Full Postcode, e.g. SY4 1HW Less error prone than asking for name of place. Some GIS can use or you can convert to Lat/Long online at doogal.co.uk Batch Geocoding

Mapping severity of footpath damage within a sensitive area.

 Location Type What location format? Considerations Lines Latitude and Longitude or Ordnance Survey Grid Reference Record as a series of individual points; make sure you know the order.

Mapping land use

 Location Type What location format? Considerations Areas Latitude and Longitude or Ordnance Survey Grid Reference Record as a series of individual points; make sure you know the order. For areas ensure points form a closed loop.

Assessing environmental quality as part of a study of deprivation

 Location Type What location format? Considerations Areas Census Output Area (or Super Output Area) Identify Census areas to be studied in advance (using secondary data). Ensure you have a map showing area boundaries.

Recording location could be done by noting down the latitude and longitude of every point where you collect data, storing locations in a GPS device or using existing boundaries (such as census output areas) to define your sampling areas.

• Adding a spreadsheet containing point data to ArcGIS Online can be done via three different routes;

With ArcGIS Online, you can use the Collector app for ArcGIS or Survey 123 to collect your data directly onto a map.

Both Collector and Survey 123 are available for Android, iOS and Windows, and allow you to collect spatial data quickly and simply - which you choose might depend on your level of expertise with GIS and the type of data and features you want to collect.

Depending on your approach to data collection will involve either visiting pre-selected locations, or recording the locations of things in the field;

Locations for measuring the size of sediments along a beach could be chosen in advance based on an appropriate sampling strategy and a GPS used to find your way to the chosen places.

Participant observation would require you to record where someone did something – this must be recorded in the field using a GPS or one of the ArcGIS Apps.

All of this can be used to create a plan of your data collection, including, what, where, and how you will be recording.

A questionnaire used as part of an investigation into the sphere of influence of a seaside town like Tenby, might include;

 Question Location or Attribute Type Recording Data Where have you come from? Location Point Record full postcode How did you get here? Attribute Text Closed question, choose from list Why have you chosen to visit Tenby? Attribute Text Open question, record full response When did you arrive? Attribute Date Record arrival date How long did it take you to get here? Attribute Float Record travel time in hours (or parts of). E.g. 3.5 hours How long are you going to stay? Attribute Integer Record number of days. E.g. 1 day

A student investigating infiltration rates in contrasting areas of a catchment might record;

 Observations or Measurements Location or Attribute Type Recording Data Location of measurement Location Point Latitude and longitude Infiltration rate (mm/hour) Attribute Float Calculated from infiltration tube measurements Soil Texture Attribute Text From soil texture test Soil Depth Attribute Integer Soil Depth (mm) Gradient Attribute Integer Measured with clinometer