ciBioBase Data Use in ArcGIS 10x Tutorial 1: Converting ciBioBase point feature grids to raster* *Requires the Spatial Analyst Extension

Export Depth, Vegetation, or Bottom Hardness (Composition) Grid Data from your ciBioBase account. Data are exported as comma delimited point features in the universal WGS84 global coordinate system.

Add filter Grid Data exports must be cleansed of 1.70E+38 No Data placeholders The Excel Filter works well to execute this. Delete all rows with this filtered value Delete all 1.70E+38 rows (select top row; hold shift key and select bottom row; hit delete key) - These are no data placeholders generated in the gridding process and are meaningless

Filter all values less than zero; change to zero Sometimes the smoothing function of kriging “undershoots” minimum values and can create negative biovolume numbers. It is impossible to have negative biovolume; rather the value should be zero Select all values less than 0; highlight top cell; change to 0; select all cells; hit Ctrl-D (fill down) - Sometimes the kriging smoothing process can undershoot the minimum value of zero. It is impossible to have negative biovolume, thus a negative number = 0; same goes with values greater than 1

Filter all values greater than 1; change to 1 Sometimes the smoothing function of kriging “overshoots” minimum values and can create biovolume numbers > 1 (or >100%). It is impossible to have biovolume greater than 1; rather the values greater than 1 should be changed to 1 Select all values greater than 1; highlight top cell; change to 1; select all cells; hit Ctrl-D (fill down) Save the text file – ready for import into ArcGIS

Add X,Y Data and specify the WGS84 coordinate system

The view of unprojected ciBioBase grid data

Right click on Layers Select a projection. UTM NAD83 is a popular US projection. Zone-based is a popular datum (MN is Zone 15) Change to meters in order to get display in meters Project the data into a meter projection (UTM is pretty standard) in the Data Frame Properties. Change the Display to Meters

http://www.ems-i.com/ If using UTMs NAD83 Datum, consult this chart to determine your zone (US Only). Datum vary widely across the globe; use one that is in accordance with your local standard

- Select the same projection Project the actual data into meters using the Conversion Tools in ArcToolbox

Activate Spatial Analyst; Convert Feature to Raster function; verify point spacing/grid cell size using the measure tool; add 0.1 as an initial buffer

10.1 increment ciBioBase gridding process uses a target grid cell size (5-m is default). Actual individual cell sizes in ciBioBase are dynamic. Underestimating actual grid cell sizes will result in a “waffle”-like grid. Iteratively change the grid cell sizes by 10ths until grid lines disappear

10.8 meter increment The conversion to raster is complete! Now a range of spatial data analyses can be conducted.