# Sensor Metadata Layers

**URL:** <https://community.purpleair.com/t/sensor-metadata-layers/157>\
**Category:** Data Layers\
**Created:** [October 27, 2021, 7:53pm UTC](https://community.purpleair.com/t/sensor-metadata-layers/157 "2021-10-27T19:53:54Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![PurpleAir](https://sea2.discourse-cdn.com/flex020/user_avatar/community.purpleair.com/purpleair/32/176_2.png) [@PurpleAir](https://community.purpleair.com/u/PurpleAir)\
**Post date:** [October 27, 2021, 7:53pm UTC](https://community.purpleair.com/t/sensor-metadata-layers/157/1 "2021-10-27T19:53:54Z")

</div>

The “Data Layer“ field determines which indices, scales, or metadata to display on the _Map Markers_, graphs, and the map legend. The default field-selection is “US EPA PM2.5 AQI“.

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## Metadata Layers

This last partition of data layers is a section of miscellaneous system-function data. Data for this section are supplied by system functions within the PurpleAir sensors. Choose a data layer from the following section to present the sensor data within the standard scale.

[**Position Rating (stars)**](https://map.purpleair.com/1/mPOSR/): This field selection displays the position rating as a measure of how accurate the map position may be.

[**Heap Memory (kB)**](https://map.purpleair.com/1/mHEAPMEM/): This field selection displays the free heap memory on the control board.

[**WiFi Signal Strength (dBm)**](https://map.purpleair.com/1/mRSSI/): This field selection displays the WiFi Signal Strength (RSSI).

[**Sensor Uptime (minutes)**](https://map.purpleair.com/1/mUPTIME/): This field selection displays the amount of time since the firmware last started up.

[**Network Latency (seconds)**](https://map.purpleair.com/1/mLATENCY/): This field selection displays the network latency in sending data to PurpleAir.

[**Analog Input (v)**](https://map.purpleair.com/1/mADC/): This field selection displays the voltage present on the ADC input.

[**Firmware Version**](https://map.purpleair.com/1/mVERSION/): This field selection displays the status of firmware versions.

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## Learn More

[Air Quality Index](https://community.purpleair.com/t/air-quality-index-aqi/111)  
[PurpleAir Map Guide](https://community.purpleair.com/t/purpleair-map-guide/90)  
[Which AQI Data Layer to Choose](https://community.purpleair.com/t/which-aqi-data-layer-to-choose/5202)