Difference between revisions of "Sample design"
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Prior to inventory, a "stratification" needs to be done. This is valid also in a complete inventory (when all stands in the analysis area are included), since some general inventory parameters are set in this part. Considering cost-efficiency, the inventory is commonly based on a two-stage sampling procedure. Here, this starts with selecting the imported stand register of interest, i.e. the analysis area to be in-field inventoried by plotwise sampling in PPS-sampled stands. | Prior to inventory, a "stratification" needs to be done. This is valid also in a complete inventory (when all stands in the analysis area are included), since some general inventory parameters are set in this part. Considering cost-efficiency, the inventory is commonly based on a two-stage sampling procedure. Here, this starts with selecting the imported stand register of interest, i.e. the analysis area to be in-field inventoried by plotwise sampling in PPS-sampled stands. | ||
| − | ==Stand Data Required== | + | ===Stand Data Required=== |
The following stand register parameters are required to enable stratification: | The following stand register parameters are required to enable stratification: | ||
* Area (productive forest land), | * Area (productive forest land), | ||
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* Tree species proportions | * Tree species proportions | ||
| − | == Classify the imported stand register into different domains== | + | === Classify the imported stand register into different domains=== |
A domain is here a certain type of forest (e.g., stands with the dominating tree species ''Pinus contorta'') where a certain inventory-scheme should be applied, e.g. securing a certain sample size. The classification is done in the same manner as the forest domain-builder in PlanWise, i.e. the user can select stand-wise properties in the register and define (by using the logical operators) the conditions of a certain domain. If the same inventory-scheme should be applied in all stands in the current analysis area, no additional domains needs to be defined. | A domain is here a certain type of forest (e.g., stands with the dominating tree species ''Pinus contorta'') where a certain inventory-scheme should be applied, e.g. securing a certain sample size. The classification is done in the same manner as the forest domain-builder in PlanWise, i.e. the user can select stand-wise properties in the register and define (by using the logical operators) the conditions of a certain domain. If the same inventory-scheme should be applied in all stands in the current analysis area, no additional domains needs to be defined. | ||
| − | ==A stratum is defined usually based on volume and age from the stand register== | + | ===A stratum is defined usually based on volume and age from the stand register=== |
The stratification is done in each domain separately. The stands (their productive forest land areas) of a certain domain are related to one of the several user-defined strata. In addition to total area, the number of stands and the area of the largest stand can be viewed in each stratum. The stratum-matrix should first be arranged according to current forest state (by number of classes and class width) and, if desirable, defined by other variables than volume and age. | The stratification is done in each domain separately. The stands (their productive forest land areas) of a certain domain are related to one of the several user-defined strata. In addition to total area, the number of stands and the area of the largest stand can be viewed in each stratum. The stratum-matrix should first be arranged according to current forest state (by number of classes and class width) and, if desirable, defined by other variables than volume and age. | ||
| − | ==When a satisfying stratification of the domain(s) has been obtained, the total number of sample stands are decided== | + | ===When a satisfying stratification of the domain(s) has been obtained, the total number of sample stands are decided=== |
''NB: There should be at least three sample stands in each stratum. Moreover, aviod extreme differences in the representative area of different strata.'' | ''NB: There should be at least three sample stands in each stratum. Moreover, aviod extreme differences in the representative area of different strata.'' | ||
| − | ==The presupposed number of plots in a sample stand is set, depending on stand characteristics (chosen by the user)== | + | ===The presupposed number of plots in a sample stand is set, depending on stand characteristics (chosen by the user)=== |
This is called the sample plot intensity-definition part. The matrix can be re-arranged as in previous parts, by selecting preferred variables and number of classes and class width. | This is called the sample plot intensity-definition part. The matrix can be re-arranged as in previous parts, by selecting preferred variables and number of classes and class width. | ||
| − | ==The sample plot size is set in a similar manner== | + | ===The sample plot size is set in a similar manner=== |
Definitions corresponds to the radius, in meters, of the circular plots. Finally, some additional settings are made, necessary in the inventory (e.g. in the sample tree sampling). Read more about the sample tree parameters 1-3 [[Field_inventory_instruction/sv#Provtr.C3.A4dsurvalet|here]]. Unless you're into "living on the edge", it is recommended you leave P1 and P3 as default and later (in field) edit P2 to obtain a certain number of sample trees per plot (on average). | Definitions corresponds to the radius, in meters, of the circular plots. Finally, some additional settings are made, necessary in the inventory (e.g. in the sample tree sampling). Read more about the sample tree parameters 1-3 [[Field_inventory_instruction/sv#Provtr.C3.A4dsurvalet|here]]. Unless you're into "living on the edge", it is recommended you leave P1 and P3 as default and later (in field) edit P2 to obtain a certain number of sample trees per plot (on average). | ||
''NB: The number of plots per stand is set considering costs and assumed losses (caused by bad decisions made from erratic forest descriptions), less than three is only considered stupid. Unless they are very large, with radius >>10 m (and in small stands, with area <0.5 ha). A corresponding line of reasoning is held for the number of sample trees per plot, where less than 0.5 is stupid. The plots are circular, however when, e.g., acting as reference ("ground truth") to remotely sensed data with certain (quadratic) pixel size, you should adjust the plot radius hereof and define radii in meters with two decimals.'' | ''NB: The number of plots per stand is set considering costs and assumed losses (caused by bad decisions made from erratic forest descriptions), less than three is only considered stupid. Unless they are very large, with radius >>10 m (and in small stands, with area <0.5 ha). A corresponding line of reasoning is held for the number of sample trees per plot, where less than 0.5 is stupid. The plots are circular, however when, e.g., acting as reference ("ground truth") to remotely sensed data with certain (quadratic) pixel size, you should adjust the plot radius hereof and define radii in meters with two decimals.'' | ||
| − | ==This part is finished by actually sampling the sample stands in each stratum (done PPS where size is the stand area)== | + | ===This part is finished by actually sampling the sample stands in each stratum (done PPS where size is the stand area)=== |
Inspect the sampled sample stands regarding, e.g., the total number and each stands corresponding stratum. When values in corresponding columns (e.g. P1-P3, Stratum, Plots, and Radius) looks ok, you can finish and lock the sample. | Inspect the sampled sample stands regarding, e.g., the total number and each stands corresponding stratum. When values in corresponding columns (e.g. P1-P3, Stratum, Plots, and Radius) looks ok, you can finish and lock the sample. | ||