SPDSS_Task89-2_CropLandUseClassificationProcedures_20060929

• Title: SPDSS Task 89.2 - Crop and Land Use Classification Procedures for Year 2001
• Description: This memorandum describes the activities conducted under Task 89: ‘Mapping of Irrigated Land Use and Irrigated Parcel Boundaries’ for year 2001 and complements the SPDSS Memoranda for Task 89.1 and Task 90.2. This memorandum also provides details on the methods used to conduct a number of Task 89 activities, including Task 89.3: Determine Irrigated Vs. Non-irrigated Lands, Task 89.4: Identify Crop Types In Each Polygon, Task 89.5: Review, Revision and Final Classification, and Task 89.6: Conduct Accuracy Assessment, as well as the results obtained from these activities for year 2001.
• Decision Support - Doc Type: Task Memorandum
• Date: 9/29/2006
• DSS Category: GIS
• DSS: South Platte
• Basin: South Platte
• Contract/PO #: C153960
• Grant Type: Non-Reimbursable
• Bill Number: SB01-157, HB02-1152, SB03-110, HB04-1221, SB05-084, HB06-1313, SB07-122
• Prepared By: Riverside Technology inc.

MEMO 89.2
2.5.2.1 Analysis of Temporal and Spectral Characteristics of Crops in the SPDSS Area
As described in Section 2.4 crop types to be classified were selected by considering the following criteria:
(1) crops and acreage reported by the Colorado Agricultural Statistics, (2) spectral characteristics of the
crops obtained from expert knowledge and research literature, and (3) input from Consumptive Use
contractor on categories of crops with similar water requirements. Based on this information, the
following crops or crop groups were classified: `Small Grains', `Dry Beans', `Corn and Sorghum', `Sugar
Beets', `Alfalfa', `Grass for Pasture and Hay', `Fallow Parcels' (for irrigated parcels), and `Vegetables'.
Although the Consumptive Use Contractor recommended that Sorghum be considered a major crop
(SPDSS Memorandum Task 54.2, page 8), the Corn and Sorghum categories were grouped into a single
category due to similar growth patterns and relatively low proportion of Sorghum with the South Platte
basin (Sorghum represented < 0.2% of all harvested crops according to 2001 Agricultural Statistics).
Spectral characteristics of major crop types in the South Platte area, as well as a brief description of the
corresponding agricultural practices are included in Appendix C. Figure 11 shows the mean temporal
NDVI trend for major crops in the SPDSS area for the year 2001. The analysis of the temporal and
spectral characteristics of crops and other cover types used information from reference parcels collected
from FSA agencies in 15 counties within the SPDSS area and other sources. In contrast to the spectral
analysis for the classification of irrigated lands (described in Section 2.5.1 above), the purpose of this
spectral analysis was to determine the spectral and temporal differences between irrigated crop types.
From Figure 11 it is evident that the multitemporal Landsat data allows for an excellent discrimination of
most of the major crop types. The only two classes that presented a challenge for the MLC algorithm due
to their similar agricultural practices were `Alfalfa' and `Grass for Pasture and Hay'. Confusion between
`Alfalfa' and `Grass for Pasture and Hay' was reduced in later classification steps and with information
from water users.
With the exception of the `Vegetable' class, all crops were classified with the MLC algorithm. The
Vegetable class constitutes a group of crops that are important as a whole in the SPDSS area but are
localized in specific areas. These vegetable crops have very diverse spectral and temporal characteristics
due to both their physiology and the agricultural practices associated with them, making them very
difficult to classify on a pixel-by-pixel basis. Alternatively, there are spectral, temporal, spatial, and
geographical indicators that make the photointerpretation of vegetable parcels possible. For example,
spectrally, some vegetable parcels have low reflectance or NDVI values due to the soil background.
From a temporal perspective, some vegetable parcels have multiple NDVI peaks during the growing
season, indicating the occurrence of multiple harvests or multiple crops. Spatially, most vegetable parcels
are small and usually located in certain areas from a geographical standpoint (e.g., along highway 85).
Therefore, vegetable parcels were designated manually from information obtained from vegetable
growers, FSA, and water users and verified through photointerpretation and analysis of NDVI imagery.
In addition to the crops described above, the following two classes were added manually in the
classification refinement process as a result of interviews with water users and field verification activities:
`Sod Farms', and `Orchard and Tree Nursery'. Because of their distinctive cutting patterns, `Sod Farms'
were identified mainly by photointerpretation of the combined Landsat and DOQQ imagery. This
interpretation was followed with field verification activities.
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