Map unit is not the same as exact soil
USDA NRCS maps delineate areas called map units. A unit can contain one to three major soil components and additional minor components. LotProfile reports the SSURGO map unit intersected by the lookup point and shows component information when the source provides it.
Read the result as: “this point falls within this mapped survey unit.” Do not read it as proof that every place on the parcel has one soil series or one set of properties.
Drainage class, hydrologic group, and slope describe different things
- Drainage class describes the natural frequency and duration of wet periods under soil-survey conditions.
- Hydrologic soil group groups soils by runoff potential when thoroughly wet; it is commonly used in watershed methods.
- Representative component slope is a source attribute for a mapped soil component. LotProfile's separate terrain slope is calculated from nearby USGS elevation samples.
A missing value means the returned source did not provide a usable value. LotProfile does not fill gaps with a guess.
Point lookup versus area of interest
A point lookup is fast and useful for orientation. A parcel or project area may cross several map units, so parcel-wide questions need a verified boundary and area analysis. USDA Web Soil Survey lets users draw an area of interest, view a soil map, run ratings, and download official data.