NDVI, scale invariance and the modifiable areal unit problem: An assessment of vegetation in the Adelaide Parklands

Hamideh Nouri; Sharolyn Anderson; Paul Sutton; Simon Beecham; Pamela Nagler; Christopher J Jarchow; Dar A Roberts

doi:10.1016/j.scitotenv.2017.01.130

NDVI, scale invariance and the modifiable areal unit problem: An assessment of vegetation in the Adelaide Parklands

Sci Total Environ. 2017 Apr 15:584-585:11-18. doi: 10.1016/j.scitotenv.2017.01.130. Epub 2017 Jan 26.

Authors

Hamideh Nouri¹, Sharolyn Anderson², Paul Sutton³, Simon Beecham⁴, Pamela Nagler⁵, Christopher J Jarchow⁶, Dar A Roberts⁷

Affiliations

¹ Department of Water Engineering and Management, University of Twente, 7500 AE Enschede, The Netherlands. Electronic address: H.Nouri@utwente.nl.
² School of Natural and Built Environments, University of South Australia, Adelaide, SA 5095, Australia. Electronic address: Sharolyn.Anderson@unisa.edu.au.
³ School of Natural and Built Environments, University of South Australia, Adelaide, SA 5095, Australia; Department of Geography and The Environment, University of Denver, Denver, CO 80208, United States. Electronic address: Paul.Sutton@du.edu.
⁴ Natural and Built Environments Research Centre, University of South Australia, Adelaide, 5095, SA, Australia. Electronic address: Simon.Beecham@unisa.edu.au.
⁵ US Geological Survey, Southwest Biological Science Center, 520 N Park Ave, Tucson, AZ 85721, United States. Electronic address: pnagler@usgs.gov.
⁶ US Geological Survey, Southwest Biological Science Center, 520 N Park Ave, Tucson, AZ 85721, United States. Electronic address: cjarchow@usgs.gov.
⁷ Geography Department, University of California, Santa Barbara, CA, United States. Electronic address: dar@geog.ucsb.edu.

PMID: 28131936
DOI: 10.1016/j.scitotenv.2017.01.130

Abstract

This research addresses the question as to whether or not the Normalised Difference Vegetation Index (NDVI) is scale invariant (i.e. constant over spatial aggregation) for pure pixels of urban vegetation. It has been long recognized that there are issues related to the modifiable areal unit problem (MAUP) pertaining to indices such as NDVI and images at varying spatial resolutions. These issues are relevant to using NDVI values in spatial analyses. We compare two different methods of calculation of a mean NDVI: 1) using pixel values of NDVI within feature/object boundaries and 2) first calculating the mean red and mean near-infrared across all feature pixels and then calculating NDVI. We explore the nature and magnitude of these differences for images taken from two sensors, a 1.24m resolution WorldView-3 and a 0.1m resolution digital aerial image. We apply these methods over an urban park located in the Adelaide Parklands of South Australia. We demonstrate that the MAUP is not an issue for calculation of NDVI within a sensor for pure urban vegetation pixels. This may prove useful for future rule-based monitoring of the ecosystem functioning of green infrastructure.

Keywords: Airborne image; Landscape ecology; Vegetation indices; Vegetation pixels; WorldView-3.