Interpreting data

Map scales and site density

The scale at which land resource data is collected (cartographic scale) is a reflection of the sampling density—the number of observations taken throughout the survey.

Map scales are indicated on soil maps and it is important to be aware of these scales, whether this is on a paper map or via a Geographical Information System (GIS) application (when viewing spatial data refer to the metadata for an indication of map scale).

For example, at a scale of 1:50,000, a 1mm line on the map represents 50 metres on the ground.

This means that while variations in soil type may appear linear on the map, in reality soils change gradually across the landscape.

Data collected at a fine scale, such as 1:10,000 provides a higher level of detail about soils than data collected at a broader scale, such as 1:100,000.

The number of sites required to accurately map an area is prescribed in the Guidelines for Surveying Soil and Land Resources.

The table below demonstrates the appropriate use of different map scales, the relationship to the density of sites and the distance on ground that corresponds to the different scales.

Scale	Appropriate use of different map scales	Density of sites	Distance in metres represented by 1 mm on the map
1:10,000 (very high intensity mapping)	Detailed farm planning Detailed suitability for specific land use	1 per 0.8–4 ha	10
1:50,000 (high intensity mapping)	Management plans for small catchments Farm planning for agriculture use—cropping	1 per 20–100ha	50
1:100,000 (Medium intensity mapping)	Management of medium catchments Planning for low intensity land use—dryland agriculture.	1 per 100–400 ha	100
1:250,000 (Low intensity mapping)	Overview of management issues for very large catchments Strategic planning for dryland agricultural uses	<1 per 100ha	250