Data set:  PEAT INVENTORY MAPS

Documentation:  Renee Johnson, Minerals Division, MN DNR, 1998

Background:  The Peat Inventory Project performed reconnaissance level surveys
of several Minnesota counties in the 1980s.  The counties included Aitkin; 
Koochiching; a portion of northern Beltrami; Lake of the Woods, except for the 
Northwest Angle; and the southwestern corner of St. Louis county.  
The information collected was presented in hardcopy reports and maps at a scale
of 1:126,720 (1/2 inch:1 mile).  The data presented on the maps were captured 
in one of two ways for use with a raster-based software package called EPPL6,
developed by the Land Management Information Center (LMIC).  Method one used a
raster overlay technique, in which a grid of 40-acre cells was manually overlain
on the peat inventory map.  Cells were encoded by deciding which determining
the mapping unit for each cell.  Method two used digitizing to capture the 
linework of the maps using an early version of Arc/INFO software.  The data
were then rasterized using EPPL6 into 10 acre cells, and then these cells were
aggregated into 40 acre cells.  Both methods brought the peat inventory data
into the larger dataset that was being developed by LMIC called MLMIS40.  Since
MLMIS40 was not rectified to real world coordinates, the MLMIS100 dataset was
created and the peat data were converted to this dataset.
Recently, the peat data were converted into both a shapefile format and to an
Arc/INFO format for use with Arcview and Arc/INFO.

PROJECTION - UTM NAD 1983 Zone 15 N

Map Legend:  The legend of the peat inventory maps captured the following types of information:
(1) basic classes of peat, mineral, water, differentiated by color on the map,
(2) peat classes defining the total depth and type of peat and the
presence or absence of a fibric moss cap.  If a cap was present, the depth was
described.  The peat classes therefore contain two sets of contour lines 
describing the depth.  The isopleths are defined by using an upper-case letter
to define the total depth of peat and a lower-case letter to define the total 
depth of the fibric moss cap.
Since the maps were captured at a 40-acre resolution, the contour lines in many
cases are no longer obvious to users of the digital data.

The mapping units for total depth of peat is as follows:
  A -   0-150 cm
  (AB - 0-300 cm -- found in one of the counties)
  B - 151-300 cm
  C - 301-450 cm
  D - 451-600 cm
  E - 601-750 cm
The type of peat is assumed to be hemic (the medium level of decomposition),
unless the mapping unit included a small "x", such as Ax, which signified that
the peat type is sapric (the most decomposed type of peat).

The mapping units for depth of the fibric moss cap (often called "raised bogs"),is as follows:
  a -  20- 60 cm
  b -  61-150 cm
  c - 151-300 cm

As presented on the peat inventory maps, the mapping units for peat are combined
to give the user the depth of peat, the type of peat, and the depth of fibric
moss caps where present.  Thus, one can find mapunits such as A, B, C, D, or E,
indicating that the peat found does not contain a fibric moss cap of any
consequence and the depth is 0-150 cm for the A unit  to 601-750 cm for the E
unit.  One can also find mapunits that define the presence of a fibric moss cap
within a peatland, such as Aa (read as 0-150 cm of peat, primarily hemic peat, 
except for the 20-60 cm cap of fibric moss peat) or Bc (read as 151-300 cm
of primarily hemic feet, except for the 151-300 cm fibric moss cap).

Digital mapping units (stored in either the pat file for coverages or in the dbf
file for shapefiles):
The attribute data includes the mapunit (the combined letters indicating depth),as well as a breakdown by total depth of peat, depth of fibric moss cap, and 
peat type.  The fields are as follows:
  NUM_MUNIT (N,2)  - numerical value of the mapping unit, county
              specific
  GEN_MUNIT (C,7)  - general mapping unit, differentiating the classes into
              peat, mineral, water, and notmap.
  MAPUNIT (C,3)    - the mapping unit, as discussed above under legend.  This 
              field stores the combination of total depth of peat and the 
              depth of the fibric moss cap.
  TOTDEP_LTR (C,1) - the first letter of MAPUNIT.
  CAPDEP_LTR (C,1) - the second letter of MAPUNIT.
  TOT_PTYPE (C,7)  - the "total type of peat", either hemic or sapric.
  CAP_PTYPE (C,7)  - the "cap type of peat", fibricm, for fibric moss.
  TOTDEPTH (C,7)   - the total depth of peat, described in ranges of values,
              such as 0-150, 151-300, or 451-600.  The units of measure are
              centimeters.    
  TOTDEP_TOP (N,3) - the first number of the range, such as 0, 151, or 451.
  TOTDEP_BOT (N,3) - the second number of the range, such as 150, 300, or 600.
  CAPDEPTH (C,7)   - the depth of the fibric moss cap, described in ranges of
              values, such as 20-60, 61-150, or 151-300.  The units of measure
              are centimeters.
  CAPDEP_MIN (N,3) - the first number of the cap range, such as 20, 61, or 151.
  CAPDEP_MAX (N,3) - the second number of the cap range, such as 60, 150, 300.