Welcome to the CHAPIS on-line Help Documentation

Table of Contents

- CHAPIS Introduction
- Getting Started
- The Map Panel
- Message Areas
      + Tool Tips
      + Hover Labels
- The Layer List
- The Toolbar
      + Navigation tools
      + Analysis tools
- Selecting A Pollutant
- Selecting An Area of Interest
- Calculating Statistics
      + Calculating Point Statistics
      + Calculating Combined Statistics
- Gridded Emissions
- The Legend
- Relevant Terms

CHAPIS Introduction

The California Air Resources Board (ARB) developed CHAPIS as an Internet-based system which provides a simplified way to look at the size and spatial distribution of air pollution emission sources in California. ARB and local air pollution agencies collect criteria and toxic emission data from air pollution sources. This information is compiled to create the California Emission Inventory. Currently, the point source criteria and toxic pollutant emissions data from the 2001 California Emission Inventory are available in CHAPIS.

The emission data mapped in CHAPIS represent a "snapshot" of the point sources contained in the 2001 ARB Emission Inventory database called CEIDARS. All of the reported mobile and area-wide emissions are reflected as gridded emissions layers in CHAPIS. For the point (industrial) sources, the data are being phased in by source categories to allow review and quality assurance, and only selected data categories are included to date. An effort was made to confirm the location of the reported point sources in the CEIDARS database. However, positional accuracy for triangle marker placement for facilities varies based on the accuracy of reported coordinates, and the accuracy and completeness of the address-matching criteria used to assign location. The data currently available in CHAPIS for point sources reflect reported emissions from approximately 1,800 individual facilities. For more information regarding the data included for facilities, refer to the point (stationary) source reference in this file.

Getting Started

The first step is to choose an administrative boundary (i.e. a County, Air Basin, Air District, or Zip Code), or region of interest. This can be accomplished from the CHAPIS launch page by using either the drop-down menus, the "clickable" map of California, or by entering a zip code into the textbox provided and pressing the "Find Zip" button. The main CHAPIS web page returns with additional choices and a map that shows all of the point sources within the selected boundary (which is highlighted in yellow) as well as surrounding areas.




The Map Panel
The Map Panel is where the map image is displayed. The map is interactive, and using the Map Tools you can zoom in and out on the map, pan around the map, or identify map features.

The information displayed on the map is dependent on:

  • Which layers are "turned on" in the layer list and
  • the scale to which you are zoomed to.

As you zoom in on the map you will reveal more detail in the form of additional data. This is due to the presence of scale-dependent map layers. Map layers that show a great amount of detail often have pre-set scales at which they become visible. This is to prevent the data from obscuring the map at small (statewide) scales. Use the Zoom In tool to increase the scale of the map until these layers are visible.

The map scale is displayed with a scale bar at the bottom left-hand corner of the map, and the message area below the map indicates the width of the map in miles.


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Message Areas

CHAPIS has three "message areas" for displaying Tool Tips, Map Feature Labels (Hover Labels), and miscellaneous messages about the results of analyses.

Tool Tips are messages about the usage of the map tools found in CHAPIS. When your mouse pointer hovers over any of the tools, the name of the tool will be displayed in the Tool Tip message area, found directly above the toolbar. When you click on a tool to select it, the Tool Tip message area displays a message about the usage of the selected tool, as shown below for the Zoom In tool. This message is always displayed in red, and persists in the Tool Tip message area to serve as a reminder of which tool is currently selected.

Hover Labels are messages that display attribute information about features on the map (in most cases it is the feature's name). This functionality is only available for a selected set of map layers - available layers are listed in a drop-down menu below the map - and works for only one layer at a time.

To view Hover Labels, simply hover your mouse over a feature on the map. The name of the feature will appear in the Hover Label message area, directly above the map.

If a Hover Label does not appear, it may be because:
  • the feature you are pointing to is not a "Hover Label Layer",
  • you have the wrong layer selected in the "Hover Label Layer" drop-down menu,
  • there are too many features in the current extent. The Hover Label will only work if there are less than 250, and more than 0 features visible in the current extent.

Miscellaneous Messages

The message area on the upper right-hand side of the web page is used to display a variety of messages, including the number of results returned by the Identify tool, the distance measured by the Measure tool, and warnings about Zip Codes that could not be found.


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The Layer List

The map displayed on this web site is composed of a number of stacked data "layers". A layer can be thought of as a collection of features with a common theme. For example, all of the State of California's major highways are contained on a single layer, as are the state's cities, major water bodies, schools and so on.

You can view a list of the map's layers by clicking the button labeled "Show Layer List". Clicking this button produces a pop-up window like the one shown on the right.

Each layer has an associated "check box" which indicates the layer's visibility - layers with a checkmark are currently visible on the map. Check boxes can also be used to turn a layer's visibility on or off . To check, or un-check a box, simply click the box with your mouse pointer. To submit changes you have made to layer visibility click the "Refresh Map" button found at the bottom of the window. This functionality gives you the ability to customize the map's appearance, displaying only the layers you want to see.

At times the layer list will include layer names that are grayed-out. This indicates that the layer's visibility is controlled by scale-dependency. When the map scale is within the layer's upper scale threshold the layer name will no longer be grayed-out, and you will be able to control it's visibility via a check-box.

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The Toolbar

The toolbar is located directly above the map and is comprised of a number of icons, each representing a map tool. The tools have been organized by functionality into the following groupings: Navigation, Analysis, and Overview Map. For instructions on how to use the tools refer to the relevant sections below.

To select a tool from the toolbar, simply click on the tool icon with your mouse pointer. Once a tool has been selected you will notice that a red box appears around it's icon; this indicates that it is the currently selected tool.

 Navigation Tools
Zoom In
 

The magnifying glass with the plus sign is used to zoom in on a specific point on the map. To use the tool, select the zoom in icon from the map tool panel, then click, or drag a box on the map. If you perform a single map click, the point on which you click becomes the center of magnification, and, subsequently, the center of the new map. By default, each click on the map with the zoom in tool increases the map scale by 50 percent.

For more accurate zooming you may choose to create a "zoom box". This is done by pressing, and holding down the left mouse button while draging the mouse. The area enclosed within the red "zoom box" will become the new extent. To finish drawing the box simply release the left mouse button.

As you zoom in on the map you will reveal more detail in the form of additional data. This is due to the presence of 'scale-dependent' map layers. Often map layers that show a great amount of detail have pre-set scales at which they become visible. This is to prevent this data from obscuring the map at small (state-wide) scales.


Zoom Out
  The magnifying glass with the minus sign is used to zoom out from a specific point on the map. To use the tool, select the zoom out icon from the map tool panel, then click or drag a box on the map. If you perform a single map click, the point on which you click becomes the center of magnification, and, subsequently, the center of the new map. By default, each click on the map with the zoom out tool decreases the map scale by 50 percent.

As with the Zoom In tool, you can more accurately zoom out by using a "zoom box". See the Zoom In tool for a detailed description of this feature.

As you zoom out, the map will display less detail as 'scale-dependent' layers turn off.


Pan
  The hand is the pan tool.  Panning is a useful function that allows you to move around the map without changing the scale. Think of it as shifting a paper map across a desktop in order to view a different portion of it. To use the pan tool select the pan icon from the map tool panel and then click, and hold down the left mouse button on the map to pan to a new area. Release the left mouse button to finish panning.

Full Extent
  The full extent tool allows you to quickly zoom out to the map's maximum extent. To use the full extent function, simply click on the full extent icon. The full map area will be displayed in the map panel.

 Analysis Tools
Identify
  The stylized "i" icon is the identify tool. This tool allows you to identify features on certain map layers. All of the features on the map have attribute data associated with them. This data can be accessed and retrieved via the identify tool. Using the tool is a two-step process. The first step is to specify which layer you wish to perform an identify function on. Below the map is a drop-down menu containing a list of identifiable map layers. Select one of these. The second step is to click on the feature you wish to identify on the map. If a feature is found at the location of your map click then the identification results are returned as seen below:
 

Circle Tool
 

The Circle tool allows you to draw a circle anywhere on the map. This tool is useful for determining whether one feature is within a given distance of another. For instance, a circle could be used to determine if a emission point source is within 1000 ft of a school.

Drawing a circle is a three step process: 1) select the circle tool 2) chose a radius from the drop-down menu found in the "Map Settings" section below the map, 3) click on the map to draw the circle. The circle will be centered around the location of you mouse click. The image below shows how the circle will appear once drawn.

 
 

There is no limit to the number of circles that can be drawn at one time. Any circles that you create will persist until they are cleared using the "Clear Circles" button .


Measure
 

The measure tool allows you to measure the distance between two points on the map. To use the measure tool, simply select the tool from the toolbar, then click on the map once to draw your first point, then click a second time to draw your second point. After the second point has been drawn, a new map will be generated showing the two points you created, connected by a line (see image below). The distance measured between these points will be displayed in the miscellaneous message area.

 

 Overview Map
Toggle Overview Map On/Off
 

Click this button once to display the Overview map - the map appear in the upper-left corner of the map panel. Click this button again to hide the Overview map.


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Selecting a pollutant
Directly below the map you will find two drop-down menus, the first of which contains a list of toxic and criteria pollutants. With this list, search criteria can be established to view only those sources emitting a selected pollutant.

Press the black arrow on the right side of the "Select a pollutant" menu to choose a pollutant to map. Before any changes take place on the map you must submit your selection by pressing the "Go" button.

Industrial (point) emissions source locations are marked using a black triangle. When a pollutant is selected the point markers are replaced with a graduated symbol that reflects the amount of emissions reported for each facility. A legend is available on-screen to identify the range of emissions associated with the marker size.

The second drop-down menu contains a list of Standard Industrial Classification (SIC) codes. With this list, search criteria can be established to differentiate between those facilities whose SIC code matches that selected, and those that do not. When a SIC code is selected only those facilities having the selected SIC code are symbolized with a black triangle - facilities with a different SIC code are "grayed-out".

Once a pollutant or a SIC code has been selected, a button labeled "Clear" will appear beside the menu. Pressing this button will clear the currently selected pollutant and/or SIC code, and refresh the map

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Selecting An Area of Interest
At the bottom of the CHAPIS web page you will find two drop-down menus, and a text box where you can enter a zip code. These features allow you to quickly zoom to an area of interest to you.
The first drop-down menu contains a list of all 58 counties in the state of California, as well as the State's 15 recognized Air Basins, and 35 Air Districts. Each category is indicated by a heading. If, for instance, you are interested in the air quality of Fresno county, you could quickly zoom to the extent of the county by selecting Fresno from the COUNTIES section of the drop down-menu . Selecting a name automatically redraws the map to your chosen extent.
The second drop-down menu contains a list of 17 regions of interest in the state of California. Selecting a name automatically redraws the map to your chosen region.
The text box allows you to enter a zip code to zoom to. Once you have finished entering your zip, press the button labeled "Go To Zip". If the zip code is found, the map will be redrawn, zoomed-in to the geographic boundaries of your zip code.

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Calculating Statistics

 Calculate Point Statistics   

This functionality allows you to generate summary statistics across all the point facilities in the view extent. These statistics include maximum emissions, average emissions, and total emissions.

The results returned from this function will differ depending on whether a pollutant has been selected or not. These difference are explained in the section below.

Note: If the number of facilities in the view extent exceeds 100 you will not be permitted to calculate statistics - the processing time needed to calculate statistics on more than 100 facilities can hinder the performance of the CHAPIS application. Zoom in on the map and re-try your request.

Calculating Statistics Without A Pollutant Selected

If a pollutant has not been selected, and there are less than 100 pollutant points in the current extent, clicking on the calculate statistics button will return results similar to that shown below:

This table provides a summary of each pollutant across all the facilities in the view extent. Statistics include the total, average, and maximum emissions for each pollutant in the extent, as well as the total cancer-potency weighted pounds.


Calculating Statistics With A Pollutant Selected

If a pollutant has been selected, and there are less than 100 pollutant points in the current extent, clicking on the calculate statistics button will return results similar to that shown below:

Summary statistics are displayed at the top of the results table, followed by a list of all of the facilities in the current extent, sorted by emissions. Each facility name is hyperlinked to the CEIDARS database, providing additional detailed information about each facility.

 Calculate Combined Statistics   
This functionality is only available when gridded emissions are visible, and allows you to generate statistics for all of the grids that fall completely within the current map view. The summary that results is shown below.
The bar graph pictured above shows the total emissions for the current pollutant, for each of the five source categories. The grid cells included in this analysis are indicated on the map with a blue box - only cells that fall within the bounds of this box are included.

In addition to the bar graph, the results page includes summary statistics for all of the point facilities that fall within the analysis area (blue box).

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Gridded Emissions

"Gridded emissions" are used as a common basis for combining all source categories onto one map view. The state is divided into a set of grid squares, which are one or more kilometers on a side. Any emissions that fall into a particular grid square add to the total emissions and corresponding color used for that grid cell on the map. Traditionally, most mobile and area wide source categories are inventoried only as county total emission estimates. So these county totals must be spatially distributed to the smaller grid areas using spatial surrogates to apportion the emissions for each source category type. For example, the distribution of population (based on the census) is used to allocate the consumer product (household) emissions into the grid cells.

The information displayed in the CHAPIS gridded emission layers comes from three major types: mobile sources (likes cars and trucks), stationary point sources (like industries at a fixed location), and area wide sources (like dispersed usage of consumer products such as hairspray). The gridded emissions divide these major types into five source categories: on road mobile sources, off road mobile sources, large industrial point sources, small commercial point sources, and area wide (dispersed) sources.

On road mobile sources include motor vehicles that customarily carry passengers or freight, and operate on public roads, such as cars, trucks, buses, and motorcycles. The information for on road sources is compiled by the Air Resources Board (ARB) using testing and research data, and data from the Department of Motor Vehicles (DMV), Caltrans, and the California Councils of Government (COGs). Models such as EMFAC2002 and Travel Demand Models are used to estimate the county total emissions annually. These are allocated to grid cells using the Direct Travel Impact Model (DTIM).

Off-road mobile sources include non road sources, such as trains, ships and boats, airplanes, cranes, construction equipment, lawn mowers, and leaf blowers. Various models such as the OFFROAD model are used to estimate the county total emissions annually. These are allocated to grid cells using various spatial surrogates, such as airport locations or light industrial zoning, for each category.

Large industrial point sources include businesses or manufacturing facilities operating at fixed locations, such as power plants or refineries. The information is compiled by each local air pollution control or air quality management district, usually through permits, throughput surveys, or other reporting requirements. The emissions are generally available for these sources for the site location of the industrial facility, so these sources can be represented both as triangular symbols on the CHAPIS map and also summarized into grid cells.

Small commercial point sources include relatively small, widespread businesses, such as gasoline stations, dry cleaners, or autobody shops. The information is sometimes available for individual sites or more often only as county total emission estimates that are spatially allocated to the grid cells using surrogates.

Area wide (dispersed) sources include widely dispersed sources such as the use of consumer products like hairspray and automotive products, and dispersed solvent use like architectural painting. These sources are estimated by the ARB and/or the local air districts. County total emission estimates are spatially allocated to grid cells using surrogates, such as using the population distribution to apportion consumer products.


Viewing Gridded Emissions with CHAPIS

To turn on the Gridded Emissions layers use the "Gridded Emissions Source Categories" menu, pictured on the left. To get this menu click the "Gridded Emissions" button found to the right of the map panel.

Use the checkboxes associated with each source category to turn on/off the visibility of that layer. Multiple gridded emissions categories can be displayed at once. Once you have made your selections click the "Refresh Map" button to close the window, and re-draw the map.

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The Legend

A facilities legend is displayed to the right of the map. This legend is used only to display the symbology of industrial (point) emissions sources.

This legend changes to reflect the current settings (i.e. whether a pollutant or SIC code has been selected from the drop-down menus at the top of the page). If a pollutant hasn't been selected, facilities are uniformly symbolized with a black triangle. Once a pollutant has been selected from the menu, the symbology changes to a black, graduated triangular symbol (pictured on left).


To view an expanded legend for all other map layers, click on the "Show Full Legend" button, found directly to the right of the facility legend. A map legend showing the symbology for all of the visible layers (pictured on right) is displayed in it's own browser window.

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Relevant Terms

This section provides definitions of some of the terms used in the CHAPIS application.

Air Basins

California is divided geographically into air basins for the purpose of managing the air resources of the State on a regional basis. Areas within each air basin are considered to share the same air masses and are therefore expected to have similar ambient air quality. The State is currently divided into 14 land-based 6air basins, along with an Outer Continental Shelf (OCS) ocean-based air basin, which is sometimes included.

Air Districts

The State is divided into 35 Air Pollution Control Districts and Air Quality Management Districts, which are also called local air districts. These agencies are county or regional governing authorities that have primary responsibility for controlling air pollution from stationary sources 

Cancer Potency Weighted Pounds

A relative index used to normalize for the widely differing toxicities (cancer potencies) of different air toxic chemicals on a pound-for-pound basis. The pounds of emissions of each carcinogenic chemical are weighted by the relative cancer potency value for that chemical.

Potency-Weighted Lbs = Emissions of Pollutant (in lbs) x Cancer Potency Value for that Pollutant x 1700.

(The 1700 is a "normalization constant" used to scale the values, based on using health-protective modeling assumptions to create a relative "score" scale, where a resultant "score" of approximately 10 or more starts to be potentially important for further review from a public health perspective).

Criteria Air Pollutant

Criteria air pollutants are those pollutants, and their precursors, for which health-based threshold standards (or "criteria") have been promulgated by the federal or state air agencies. The staff at the California Air Resources Board compiles data to create the criteria pollutant emission inventory which includes information on the emissions of reactive organic gases (ROG), oxides of nitrogen (NOx), oxides of sulfur (SOx), carbon monoxide (CO), and particulate matter (PM10). 

Area-wide (Dispersed) Sources of Emissions

Area-wide sources include widely dispersed sources such as the use of consumer products (hairspray, home automotive products, home cleaners, etc.) and other dispersed solvent uses, such as painting (sometimes referred to as architectural coating). Area-wide emission sources are generally estimated at a county-level of resolution, then spatially allocated to smaller grid squares using spatial allocation factors that are based on a surrogate for the activity, such as using the distribution of population to allocate consumer product usage.

Emission Inventory

The California Air Resources Board has collected information on emissions from air pollution sources since 1969. This information is periodically compiled by State and local air pollution control agencies to create an emission inventory; an important building block in the development of the State's air pollution control program.

The emission inventory includes information on the emissions of criteria and toxic air pollutants. Criteria pollutants include reactive organic gases (ROG), oxides of nitrogen (NOx), oxides of sulfur (SOx), carbon monoxide (CO), and particulate matter of diameter 10 microns or less (PM10). Toxic data available within CHAPIS were collected in response to Assembly Bill (AB) 2588 (Connelly), the Air Toxics "Hot Spots" Information and Assessment Act. Criteria and toxic data are gathered on an ongoing basis and stored in the California Emission Inventory Development and Reporting System (CEIDARS).

Gridded Emissions

Gridded emissions are used as a common basis for combining all source categories onto one map view. The state is divided into a set of grid squares, which are one or more kilometers on a side. Any emissions that fall into a particular grid square add to the total emissions and corresponding color used for that grid cell on the map. Traditionally, most mobile and area-wide source categories are inventoried only as county-total emission estimates. So these county totals must be spatially distributed to the smaller grid areas using spatial surrogates to apportion the emissions for each source category type. For example, the distribution of population (based on the census) is used to allocate the consumer product (household) emissions into grid cells.

Mobile Sources of Emissions -- On-Road Mobile and Off-Road Mobile Sources

Mobile sources can be either on-road or off-road mobile sources. On-road mobile sources include motor vehicles that customarily carry passengers or freight, and operate on public roads, such as cars, trucks, buses, and motorcycles. Off-road mobile sources include trains, ships and boats, airplanes, cranes, construction equipment, lawn mowers, and leaf blowers.

Point (Stationary) Sources of Emissions -- Industrial and Small Commercial Facilities

The point, or stationary, sources of emissions include businesses and manufacturing facilities operating at a fixed location.

Large industrial point sources include industrial or manufacturing facilities, such as electric power plants or refineries. The information is compiled by each local air pollution control or air quality management district, usually through permits, throughput surveys, or other reporting requirements. The emissions are generally available for these sources for the site location of the industrial facility, so these sources can be represented both as triangular symbols on the CHAPIS map and also summarized into grid cells.

Small commercial point sources include relatively small, widespread businesses, such as gasoline stations, dry cleaners, or autobody shops. The information is sometimes available from the districts for individual sites that can be represented as point sources, or more often are estimated only as county-total emission estimates that are spatially allocated to grid cells using surrogates.

The information currently available in CHAPIS reflects reported emission data from approximately 1,800 industrial facilities as point sources. The point sources are being phased in over time by selected source categories, to allow for review and quality assurance. (See “Selected Data” for more information on which source categories are included). To best represent the geographic location of industrial point sources, an effort was made to assess the accuracy of a facility’s reported geographic coordinates. Where geographic coordinates were determined to be reasonably accurate, these coordinates were used to assign geographic location. When coordinates were found to be incomplete or inaccurate, and if facility address, city, and zip code information was determined to be accurate and sufficiently complete, then geographic location was assigned based on matching reported facility addresses to map address ranges.

Selected Data

CHAPIS includes all of the on-road and off-road mobile sources, and all of the area-wide sources, as gridded emissions. For the point (stationary) sources, represented as triangles on the CHAPIS map, the facilities are being phased in over time by source categories to allow for review and quality assurance. To date, CHAPIS includes the following stationary source (facility) information:

1. Criteria air pollutant emissions from facilities that emit 10 or more tons per year of ROG, NOx, SOx, CO, or PM10;
2. Toxic air pollutant emissions from power plants (50 megawatts or more) and refineries; and
3. Toxic air pollutant emissions from facilities that conducted health risk assessments under the Air Toxics “Hot Spots” Program and fall into the categories of (a) metal fabrication facilities, (b) aerospace/electronics facilities, and (c) chemical plants. The ARB is continuing to collaborate with the California Air Pollution Control Officers Association (CAPCOA) regarding the inclusion of additional toxics emission facilities. Over the next several months we anticipate adding information for the other facilities that conducted health risk assessments, as well as locations of gasoline stations and other small commercial categories.

Standard Industrial Classification (SIC) Code

A statistical classification standard underlying all establishment-based federal economic statistics classified by industry. The SIC two-digit summary group classification is used in CHAPIS.

Toxic Air Pollutant

Toxic air pollutants are chemicals that have the potential to cause adverse health effects, such as cancer, birth defects, and organ damage. Toxics emission inventory data included in CHAPIS are from the 2001 database year of the CEIDARS emission inventory and reflect the most current data available. However, the emissions in the database may be derived from earlier or more recent emission inventory reporting years. The toxics data are submitted to the ARB by the air pollution control and air quality management districts as a requirement of the Air Toxics "Hot Spots" Program (sometimes referred to as AB 2588). The "Hot Spots" Program requires emission inventory updates every four years for the larger facilities if there have been substantial increases in their previously reported emissions. Toxic air contaminants are also identified and controlled through the Toxic Air Contaminant Identification and Control Program (sometimes referred to as AB 1807).

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