A procedure to design random plots in GIS forest stratification map using the ArcGIS programme

1. Creationof random points
Box 9. A procedure todesignrandomplotsinGISforeststratificationmapusing the ArcGISprogramme
Step1: Dissolve spatiallydiscreteforestblocksbyforeststatus.
The purpose of thisstepis to create homogeneousstrataof forests.Spatiallydiscrete forest
blockswithsimilarstrataare combinedintoone stratum.Use the followingtwostepsinArcGIS:
• Selectthe data layerthatcontains polygonsof foreststatusblocks
• Use Dissolve tocombine all the polygonsthathave the same status:
- Selectthe Dissolvetool
- In the dialogue box shownbelow,selectthe datalayerthat contains the foreststatusin
InputFeature.Specifythe outputfile inOutputFeature Class.Selectthe foreststatusfieldunder
Dissolve Field.ClickOK.
Step2: Enterthe numberof requiredsampleplotsforeachforeststratuminthe attribute table of the
foreststratificationmap.
A field‘Number_of_Plots’(of type –numeric) iscreatedinthe attribute table of the GISmap
layer,containingthe dissolvedstratum.Thenenterintothisfieldthe numberof requiredsample plots
for eachstratum determined.

2. Step3: A networkof random sample plotsare createdandoverlaidonthe dissolvedforeststratum
(polygons):
In ArcGIStool,selectCreate RandomPoints,asshownbelow:
- SelectOutputlocation
- Selectmap layerof dissolvedstratum
- Numberof Points:SelectFieldandthenselectfield‘Number_of_Plots’
- Enteran appropriate value forMinimumAllowedDistance.Thisisthe smallestdistance allowed
betweentworandomlyplacedplots.
- ClickOK

3. Random sampling of points QGIS
1. Open QGIS and load the iba.shp polygon layer. This layer is the study area you will
conduct the sampling, we will create a new point layer of 100 random points within the boundary
of the polygon.
2. In the Menu select Vector ‣Research Tools ‣ Random Points.
3. Select iba as your Input Boundary Layer.
4. Under the Unstratified Sampling Design, type 100 in the Use this number of points.
5. In the Output Shapefile click Browse and create a new Shapefile
as random_100pts.shp. Click OK.

4. 6. Click Yes to add the new layer to your Map Canvas. Click Close to close the Random
Points window.

5. The created point layer has 100 randomly placed points within the boundary of the polygon.