High Resolution Greenspace Land Cover in Philadelphia, Pennsylvania

This dataset provides a high resolution (1-m) land cover map for Philadelphia, Pennsylvania in the United States of America during the summer of 2017. This dataset was created to differentiate two types of green space in Philadelphia: tree and grass cover. The dataset includes four numerically coded land cover classes.

Input data:

This classification is derived from National Agriculture Imagery Program (NAIP) 1-m aerial imagery captured in the State of Pennsylvania during June of 2017. To improve classification accuracy, NAIP data was stacked with Sentinel-2 level 1C 10-m and 20-m data using the .addBands() function in Google Earth Engine. For the Sentinel-2 data, a median composite was calculated from cloud-masked images collected between April and October of 2017. Sentinel-2 input bands included blue, green, red, red edge 1, red edge 2, red edge 3, near infrared, and shortwave infrared 1. An additional normalized difference vegetation index (NDVI) was calculated from the NAIP and Sentinel-2 bands using the formula:

NDVI = (Near infrared - Red) / (Near infrared + Red)

Classification methods:

We classified the input data using a Random Forest classifier with 200 trees. Data was classified into four coded land cover classes:

1 - Tree

2 - Grass

3 - Human-built structures

4 - Open water

8,961 land cover reference points were collected with 70% used to train and 30% to test the classifier. Results were smoothed using a 3x3 square kernel based on the mode of a pixel’s neighbors.

Accuracy:

Measures of accuracy including overall accuracy and per class user’s (UA) and producer’s accuracy (PA) of the random forest classifier were calculated.

Overall accuracy: 93%

Tree: UA = 89.73% PA = 93.90%

Grass: UA = 93.41% PA = 88.21%

Human-built structures: UA = 98.28% PA = 97.47%

Open water: UA = 93.56% PA = 98.95%

Code link:

The Google Earth Engine code used in this analysis is publicly available.

https://code.earthengine.google.com/32d3a77e70955a6279ec22233778bd8f

Data for download:

Two files are available for download.

1. Philadelphia_classification_points.zip

Contains a shapefile of the 8,961 reference points used to train and test the classifier.

       2. Philadelphia_Landcover_2017.zip

Contains a GEOTIFF of the classified image over Philadelphia, Pennsylvania for the summer of 2017.