Texture Analysis for Mapping Tamarix parviflora Using Aerial Photographs along the Cache Creek, California

Abstract

Natural color photographs were used to detect the coverage of saltcedar, Tamarix parviflora, along a 40 km portion of Cache Creek near Woodland, California. Historical aerial photographs from 2001 were retrospectively evaluated and compared with actual ground-based information to assess accuracy of the assessment process. The color aerial photos were sequentially digitized, georeferenced, classified using color and texture methods, and mosaiced into maps for field use. Eight types of ground cover (Tamarix, agricultural crops, roads, rocks, water bodies, evergreen trees, non-evergreen trees and shrubs (excluding Tamarix)) were selected from the digitized photos for separability analysis and supervised classification. Due to color similarities among the eight cover types, the average separability, based originally only on color, was very low. The separability was improved significantly through the inclusion of texture analysis. Six types of texture measures with various window sizes were evaluated. The best texture was used as an additional feature along with the color, for identifying Tamarix. A total of 29 color photographs were processed to detect Tamarix infestations using a combination of the original digital images and optimal texture features. It was found that the saltcedar covered a total of 3.96 km(2) (396 hectares) within the study area. For the accuracy assessment, 95 classified samples from the resulting map were checked in the field with a global position system (GPS) unit to verify Tamarix presence. The producer's accuracy was 77.89%. In addition, 157 independently located ground sites containing saltcedar were compared with the classified maps, producing a user's accuracy of 71.33%.

Mapping Invasive Tamarisk (Tamarix): A Comparison of Single-Scene and Time-Series Analyses of Remotely Sensed Data

“…Ge et al [32] analyzed color aerial photographs at 1-m 2 resolution using a texture analysis for tamarisk in northern California. The photographs were acquired in April and the mean grey-level values were calculated for 60 pixels representing eight cover types.…”

Salt cedar areawide pest management in the western USA.

“…The coupling of colour and texture analysis was first used to identify, classify and map invasive T pamiflora during spring bloom, along a 50-mile (80-km) segment of Cache Creek in central CA, with an estimated 90% accuracy (Ge et al, 2006).…”

“…Colour patterns alone were not adequate to separate and classify the salt cedar from the other categories of habitat, and thus more complex methods of analysis were required. To distinguish salt cedar from associated vegetation and background required the combined use of colour and texture analysis to provide an adequate measure of salt cedar density (see Ge et al, 2006).…”

“…Comparisons made between this automated salt cedar recognition process from the photographs resulted in a classification providing 90% accuracy through actual field validation (Ge et al, 2006). These classified images were then mosaiced across the study area in order to provide comprehensive infestation maps and to estimate the invasive salt cedar cover in a 40-km test area of the Cache Creek drainage.…”

Integrating Remote Sensing with Species Distribution Models; Mapping Tamarisk Invasions Using the Software for Assisted Habitat Modeling (SAHM)

“…Conventional classification analyses and remote sensing software have had marginal success [3][4][5] . Several recent studies have explored non-traditional approaches to detect invasive plants using remote sensing data 1,6 .…”