The survey design is a plan for selecting the sample appropriately so that it provides valid data for developing accurate estimates for the entire population or area of interest.  At this point in the design process it is assumed that the folloing have been completed:

1. Established the monitoring objectives
2. Identified Resource Characteristics
3. Identified Institutional constraints requiring consideration
4. Defined the target population
5. Specified Subpopulations, Domains and Stratification
6. Created a sampling frame for all units of the target population from which to select the sample
7. Selected a GRTS survey design for the selection of sample of units from this frame
8. Selected a strategy for allocation of sampling efforts in space and time
9. Established sample size(s)

Additional information on each of these items is available on Design Specifics

Utah Ecoregion Survey Design Example

Purpose: Illustrate area GRTS survey design for Omernik level 3 ecoregions within Utah.

This information is presented as an example and recommended format for documenting a GRTS design. It is recommended that this example be followed, prior to initiating efforts to produce a design to meet a particular objective. Due to the randomization scheme within psurvey.design, each execution of the R code will produce a different set of sampling points and output files and will not exactly reproduce the example files.

Materials needed for this example:

• R version 2.2.1
• psurvey.design 2.2.1 + sp package
• R script or text file: utahlevel3design.R
• Frame materials as ArcGis files:
• eco_l3_ut.dbf
• eco_l3_ut.prj
• eco_l3_ut.sbn
• eco_l3_ut.sbx
• eco_l3_ut.shp
• eco_l3_ut.shx
• Download Example Files

Example includes:

There are seven Level 3 Ecoregions is Utah:

• Central Basin and Range
• Colorado Plateaus
• Mojave Basin and Range
• Northern Basin and Range
• Southern Rockies
• Wasatch and Uinta Mountains
• Wyoming Basin

Design File Documentation would routinely begin here:

Contact:

Description of Sample Design

Survey Design: A Generalized Random Tessellation Stratified (GRTS) survey design for a linear stream resource is used for this example. The GRTS design includes reverse hierarchical ordering of the selected sites.

Target population: All area within State of Utah..

Sample Frame: GIS Ecoregion coverage from HELP. Utah Ecoregion Map

Sample Frame Summary

The total area within Utah is .

I. Equal Probability GRTS Survey Design

Stratification: None

Expected sample size: 115 sites

Oversample: None

Site Use: The base design has 115 sites. Sites are listed in SiteID order and must be used in that order. All sites that occur prior to the last site used must have been evaluated for use and then either sampled or reason documented why that site was not used.

Site Selection Summary

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II. Stratified GRTS Survey Design

Stratification: Stratification by ecoregion, with equal probability selection within Ecoregion.

Expected sample size: Ten or 25 sites per Ecoregion, total 115 sites (see summary table).

Oversample: None.

Site Use: The stratified design has 115 sites. Sites are listed in SiteID order and must be used in that order. All sites that occur prior to the last site used must have been evaluated for use and then either sampled or reason documented why that site was not used.

Site Selection Summary

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III. Unequal Probability GRTS Survey Design

Stratification: None, .

Expected sample size: 115 sites with approximate number of sites for each Level 3 Ecoregion (see Summary table).

Oversample: None.

Site Use: The unequal probability design has 115 sites. Sites are listed in SiteID order and must be used in that order. All sites that occur prior to the last site used must have been evaluated for use and then either sampled or reason documented why that site was not used.

Site Selection Summary

III. Panels for surveys over time with unequal Probability GRTS Survey Design with Oversample

Stratification: None, .

Expected sample size: Five Panels with 50 Sites/Panel (see Summary table).

Oversample: 100.

Site Use: The unequal probability design has 115 sites. Sites are listed in SiteID order and must be used in that order. All sites that occur prior to the last site used must have been evaluated for use and then either sampled or reason documented why that site was not used.

Site Selection Summary

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