Julie Lovesay Chief Directorate: National Geo

Julie Lovesay
Chief Directorate: National Geo-spatial Information
Introduction
The Chief Directorate: National Geo-Spatial
Information (CD:NGI) is mandated under the Land
Survey Act to conduct topographical surveys as
required
This has traditionally been done in the form of
1:50 000 topographical maps and a series of shapefiles
Recently, CD:NGI has embarked on a national land
cover and land use program with then intention of
producing maps at a scale of 1:100 000
Land Cover
Land cover is the observed (bio)physical cover on the
earth's surface
Eg, is the land covered by grass, by trees, by water, or
by large buildings surrounded by a lawn?
Land Use
Land use is characterized by the arrangements,
activities and inputs people undertake in a certain land
cover type to produce, change or maintain it.
Definition of land use in this way establishes a direct
link between land cover and the actions of people in
their environment.
For example is the land being used for commercial
purposes (stores, office buildings, apartments, etc.) or
for industrial purposes (factories, assembly
plants)? Or is the land being used for recreational or
agricultural purposes?
Relationship between land cover
and land use
“Grassland/Graminoids" is a land cover term, while
golf course, sports field, Botanical Gardens, Game
Farm, or undeveloped lands refer to the use of a grass
cover;
“Recreation and Leisure" is a land use term that may
be applicable to different land cover types: for instance
sandy surfaces like a beach; a built-up area like a
theme park; etc
Pilot Areas
King Sabata Dalindyebo & Qaukeni (EC)
Maluti a Phofung & Dihlabeng (FS)
Knysna West & Swellendam (WC)
Mogalakwena & Tubatse(LP)
Land Cover
Raster based product, i.e. made up of pixels in
different colours and each colour represents a class
The legend was based on the FAO land cover
classification system (LCCS), but only mapped to the
second level (32 classes)
Pixel size: 10m
Minimum mapping unit: 1 hectare
Land Use
Vector based (shapefiles)
Polygons only (no points or lines)
Consists of 60 classes (14 main classes) – this needs to be
refined as there is no standard land use classification
legend.
Can have more than one land use per polygon
Is not constrained to scale
Mapped at various levels depending on whether its urban or
rural
Is more difficult than land cover to map – not just visible
from imagery
Main users will be planners
Land Use – Level 1 classes
1
Agriculture & Fisheries
8 Community Services
2 Forestry
9 Commercial
3 Conservation
10 Industrial & Storage
4 Mining
11 Recreation & Leisure
5 Transport
12 Protection Services
6 Utilities & Infrastructure
13 Undeveloped Land
7 Residential
14 Water
Issues and problems encountered
wrt Land Use Classification
The data does not exist – municipalities don't have up to
date, correct data
Land use at the proposed level is constantly changing
How to deal with multiple land uses over many levels e.g.
CBD often has shops on ground floor, offices above and
residential at the top
Also, multiple uses within 1 erf – e.g. farm with workers
housing, guest house, grazing and agriculture, possibly a
small factory
Expensive to map – cannot be mapped from digital imagery
Mapping in rural areas – adds to cost, use of 500m/1km
grid not ideal
Field Verification & Accuracy
Assessment
The accuracy of the land cover and land use data sets
cannot be verified without a field verification
The tender specifies a confidence level of 80% or
higher for the land cover and land use
The field verifier is required to visit at least 10
instances of each class, and if there is less than 10, they
must visit all of them.
Results of the field verification
On average the land cover accuracy was above 80%,
but the land use ranged from 67-77%