AlleghenyCounty_TreeCanopyChange_2015_2020_202401
Identification_Information:
Citation:
Citation_Information:
Publication_Date:202401
Title:
AlleghenyCounty_TreeCanopyChange_2015_2020_202401
Geospatial_Data_Presentation_Form:vector digital data
Online_Linkage: https://www.pasda.psu.edu
Description:
Abstract: 
With the size of the study area measured at approximately 743.96 square miles, a cost-effective and accurate strategy for assessing tree canopy change is the use of a height-based canopy extraction model from LiDAR data.
Purpose: 
The purpose of this project was to conduct an assessment of tree canopy change that occurred between 2015 and 2020 utiliing LiDAR data and a previously prepared canopy dataset. Comprehensive canopy change statistics are provided for various geographies down to the parcel-level scale.
Status:
Maintenance_and_Update_Frequency:Unknown
Spatial_Domain:
Bounding_Coordinates:
West_Bounding_Coordinate:-80.368057
East_Bounding_Coordinate:-79.677731
North_Bounding_Coordinate:40.682774
South_Bounding_Coordinate:40.185618
Keywords:
Theme:
Theme_Keyword_Thesaurus:None
Theme_Keyword:City of Pittsburgh
Theme_Keyword:Pennsylvania
Theme_Keyword:Allegheny County
Theme_Keyword:Tree Canopy
Theme_Keyword:Tree Canopy Change
Access_Constraints:None
Use_Constraints: 
As determined by the City of Pittsburgh, Pennsylvania
Point_of_Contact:
Contact_Information:
Contact_Organization_Primary:
Contact_Organization:Davey Resource Group, Inc.
Contact_Person:Kerry Gray
Contact_Position:ISA Certified Arborist
Contact_Voice_Telephone:734-249-3576
Contact_Electronic_Mail_Address:kerry.gray@davey.com
Hours_of_Service:8:00 am - 5:00 pm EST
Point_of_Contact:
Contact_Information:
Contact_Organization_Primary:
Contact_Organization:Davey Resource Group, Inc.
Contact_Person:Kerry Gray
Contact_Position:ISA Certified Arborist
Contact_Voice_Telephone:734-249-3576
Contact_Electronic_Mail_Address:kerry.gray@davey.com
Hours_of_Service:8:00 am - 5:00 pm EST
Native_Data_Set_Environment:
Version 6.2 (Build 9200) ; Esri ArcGIS 10.9.1.28388
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Data_Quality_Information:
Attribute_Accuracy:
Quantitative_Attribute_Accuracy_Assessment:
Attribute_Accuracy_Explanation: 
Canopy change acreage is calculated using the ArcGIS field calculator.
Lineage:
Process_Step:
Process_Description: 
Tree canopy was extracted from LiDAR data collected in the fall of 2019 and spring of 2020 in ArcMap. A digital surface model (DSM) was created by interpolating the maximum values of the first returns of each laser pulse across a 3-foot grid surface (raster). A speckled output was created because some pulses can entirely or partially pass-through tree canopy before detecting a return, so maximum focal statistics in a 3 by 3 rectangular grid window were applied to the DSM to create a smooth surface. 
Another raster representing the elevations of solid surfaces which LiDAR does not penetrate - usually ground and buildings, but occasionally dense evergreens as well, was created by interpolating the minimum values of the last returns (which are also the first return in instances of single return). Mean focal statistics in a 3 by 3 cell window were applied to this raster. The last return raster was subtracted from the first return raster, creating a canopy height model (CHM) – a representation of the heights of objects with complex return structures above the ground. In addition to trees, this includes built structures such as power lines, poles, transmission towers, gantries, etc. The edges of buildings also appeared in the CHM as a result of different cell assignment and focal statistics types applied to the first and last return rasters. The heights of dense evergreens were underestimated due to the inability of LiDAR to penetrate to the ground for a proper base for height.
A constant raster of CHM cells with a height greater than 15 feet was created. Holes less than 500 square feet were filled to eliminate dubious small gaps while preserving discernable canopy gaps. This raster was then shrunk by 2 cells and expanded back by 2 cells. This process eliminated narrow or small features such as building edges, power lines, and poles. This raster was then converted into a vector polygon format for editing.
Process_Step:
Process_Description: 
The manual QC process was completed at a scale of 1:2,000 with reference to September 2021 Nearmap imagery and the CHM within ArcMap. In this process, remaining built structures were removed, dense evergreens were drawn in, and points were placed on missing smaller trees which would later be buffered by 9 feet. Editing preserved consistency with the LiDAR data – losses of trees that had occurred between the LiDAR and imagery flights were not removed from the data. Following primary QC, a secondary QC process was conducted by another editor.
Process_Step:
Process_Description: 
Following the completion of the 2020 canopy layer, an updated canopy change layer was created. The ”No Change” and “Gain” classes were exported from the 2010 to 2015 change dataset and then dissolved without multipart features to create a dataset only representing 2015 canopy. The “Union” tool within ArcMap was used to create a dataset representing canopy change by inputting the 2015 and completed 2020 canopy datasets. “Multipart to Singlepart” was then ran on the output. “Gain” polygons less than 30 square feet were removed from the dataset, and “Loss” polygons less than 30 square feet were recoded as “No Change.” The layer was then dissolved by the change class without multipart features. The “No Change” polygons less than 30 square feet were recoded as “Loss” and the layer was dissolved again.
Process_Step:
Process_Description: 
Dated methodology of previous canopy assessments left many herbaceous and shrubby areas, especially within and around forests, classified as tree canopy. These errors of commission resulted in egregious amounts of false loss in the 2015 to 2020 canopy change layer. These false loss polygons were removed from the dataset. To accomplish this efficiently and effectively, forest classes in the 2011 National Land Cover Dataset (NLCD) were quickly edited to remove forests that had since been cleared and forests with apparent thinning, and to add in additional areas where false loss was observed. Loss polygons centrally located within these areas were flagged as dubious. Dubious losses greater than 0.2 acres were exported out and polygons that appeared to be mostly tree canopy in 2015 NAIP imagery were unflagged as dubious. The opposite was done for all other loss polygons greater than 0.2 acres, where polygons that were mostly not tree canopy in 2015 were flagged as dubious. Losses greater than 0.2 acres accounted for 29% of the total loss area identified before the loss QC process. Of these larger losses, it was found that the edited NLCD forests were about 80% successful at classifying losses as true or false. All dubious losses were then removed from the dataset.
At the risk of overcorrecting losses, false gains, while not nearly as egregious as false losses, were also corrected. These omissions in the 2015 assessment were common amongst lower trees, lighter colored trees, tree canopy along railways and rivers, and in areas of cloud cover in the NAIP imagery. Points were placed on these large and/or obvious false gain polygons, and they were recoded as “No Change” and the layer was dissolved again.
Process_Step:
Process_Description: 
Metadata created.
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Spatial_Data_Organization_Information:
Direct_Spatial_Reference_Method:Vector
Point_and_Vector_Object_Information:
SDTS_Terms_Description:
SDTS_Point_and_Vector_Object_Type:GT-polygon composed of chains
Point_and_Vector_Object_Count:570207
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Spatial_Reference_Information:
Horizontal_Coordinate_System_Definition:
Planar:
Map_Projection:
Map_Projection_Name:NAD 1983 StatePlane Pennsylvania South FIPS 3702 Feet
Lambert_Conformal_Conic:
NAD 1983 StatePlane Pennsylvania South FIPS 3702 Feet
Standard_Parallel:39.93333333333333
Standard_Parallel:40.96666666666667
Longitude_of_Central_Meridian:-77.75
Latitude_of_Projection_Origin:39.33333333333334
False_Easting:1968500.0
False_Northing:0.0
Planar_Coordinate_Information:
Planar_Coordinate_Encoding_Method:coordinate pair
Coordinate_Representation:
Abscissa_Resolution:0.000000026907964745248598
Ordinate_Resolution:0.000000026907964745248598
Planar_Distance_Units:foot_us
Geodetic_Model:
Horizontal_Datum_Name:D North American 1983
Ellipsoid_Name:GRS 1980
Semi-major_Axis:6378137.0
Denominator_of_Flattening_Ratio:298.257222101
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Entity_and_Attribute_Information:
Detailed_Description:
Entity_Type:
Entity_Type_Label:AlleghenyCounty_TreeCanopyChange_2015_2020_202401
Attribute:
Attribute_Label:FID
Attribute_Definition: 
Internal feature number.
Attribute_Definition_Source: 
Esri
Attribute_Domain_Values:
Unrepresentable_Domain:
Sequential unique whole numbers that are automatically generated.
Attribute:
Attribute_Label:OBJECTID
Attribute_Definition: 
Internal feature number.
Attribute_Definition_Source: 
Esri
Attribute_Domain_Values:
Unrepresentable_Domain:
Sequential unique whole numbers that are automatically generated.
Attribute:
Attribute_Label:SHAPE
Attribute_Definition: 
Feature geometry.
Attribute_Definition_Source: 
Esri
Attribute_Domain_Values:
Unrepresentable_Domain:
Coordinates defining the features.
Attribute:
Attribute_Label:Change
Attribute:
Attribute_Label:Shape_Leng
Attribute:
Attribute_Label:SHAPE_Area
Attribute_Definition: 
Area of feature in internal units squared.
Attribute_Definition_Source: 
Esri
Attribute_Domain_Values:
Unrepresentable_Domain:
Positive real numbers that are automatically generated.
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Distribution_Information:
Distributor:
Contact_Information:
Contact_Organization_Primary:
Contact_Organization:Tree Pittsburgh
Contact_Person:Matthew Erb
Contact_Position:Senior Director of Science, Policy, and Planning
Contact_Address:
Address_Type:physical
Address: 
32 62nd Street
City:Pittsburgh
State_or_Province:Pennsylvania
Postal_Code:15201
Country:US
Contact_Voice_Telephone:412-781-8733 x202
Contact_Electronic_Mail_Address:matt@treepittsburgh.org
Distribution_Liability: 
As determined by the City of Pittsburgh, Pennsylvania
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Distribution_Information:
Distributor:
Contact_Information:
Contact_Organization_Primary:
Contact_Organization:Pennsylvania Spatial Data Access (PASDA)
Contact_Address:
Address_Type:mailing and physical address
Address: 
115 Land and Water building
City:University Park
State_or_Province:Pennsylvania
Postal_Code:16802
Country:United States
Contact_Voice_Telephone:(814) 865 - 8792
Contact_Electronic_Mail_Address:pasda@psu.edu
Distribution_Liability: 
The USER shall indemnify, save harmless, and, if requested, defend those parties involved with the development and distribution of this data, their officers, agents, and employees from and against any suits, claims, or actions for injury, death, or property damage arising out of the use of or any defect in the FILES or any accompanying documentation. Those parties involved with the development and distribution excluded any and all implied warranties, including warranties or merchantability and fitness for a particular purpose and makes no warranty or representation, either express or implied, with respect to the FILES or accompanying documentation, including its quality, performance, merchantability, or fitness for a particular purpose. The FILES and documentation are provided "as is" and the USER assumes the entire risk as to its quality and performance. Those parties involved with the development and distribution of this data will not be liable for any direct, indirect, special, incidental, or consequential damages arising out of the use or inability to use the FILES or any accompanying documentation
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Metadata_Reference_Information:
Metadata_Date:20240103
Metadata_Contact:
Contact_Information:
Contact_Organization_Primary:
Contact_Organization:Davey Resource Group, Inc.
Contact_Person:Nicholas Antenucci
Contact_Position:GIS Technician
Contact_Address:
Address_Type:unknown
Address: 
295 South Water Street
City:Kent
State_or_Province:OH
Postal_Code:44340
Contact_Voice_Telephone:330.673.5685 ext. 8701
Contact_Electronic_Mail_Address:nicholas.antenucci@davey.com
Hours_of_Service:8:00 am - 4:30 pm EST
Metadata_Standard_Name:FGDC Content Standard for Digital Geospatial Metadata
Metadata_Standard_Version:FGDC-STD-001-1998
Metadata_Time_Convention:local time
Metadata_Use_Constraints:
As determined by the City of Pittsburgh, Pennsylvania
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