ARM TR-064

> Tower Camera Handbook
>
> January 2005
>
> D. Moudry
>
> Work supported by the U.S. Department of Energy,
>
> Office of Science, Office of Biological and Environmental Research

# Contents {#contents .Heading-Front}

[1. General Overview 1](#general-overview)

[2. Contacts 1](#contacts)

[3. Deployment Locations and History
1](#deployment-locations-and-history)

[4. Near-Real-Time Data Plots 2](#near-real-time-data-plots)

[5. Data Description and Examples 2](#data-description-and-examples)

[6. Data Quality 4](#data-quality)

[7. Instrument Details 5](#instrument-details)

# General Overview

The tower camera in Barrow provides hourly images of ground surrounding
the tower. These images may be used to determine fractional snow cover
as winter arrives, for comparison with the albedo that can be calculated
from downward-looking radiometers, as well as some indication of present
weather. Similarly, during spring time, the camera images show the
changes in the ground albedo as the snow melts. The tower images are
saved in hourly intervals. In addition, two other cameras, the skydeck
camera in Barrow and the piling camera in Atqasuk, show the current
conditions at those sites.

# Contacts

## Mentor

Dana Moudry

University of Alaska Fairbanks

Geophysical Institute

903 Koyukuk Dr.

Fairbanks, AK 99775-7320

Phone: (907) 474-6639

Fax: (907) 474-7290

Email: <drm@gi.alaska.edu>

## Instrument Developer

Three different models of the Axis cameras are deployed at the North
Slope of Alaska (NSA) site: Axis 200+, Axis 2420, and Axis 2120. The
camera manuals may be found on the Axis website: www.axis.com.

# Deployment Locations and History 

The tower camera is deployed at the Barrow facility in the NSA locale.
Status as of January 27, 2005:

+-------+-------+--------------------------+-------------+-----------+
| C     | Loc   | Current image            | Camera      | H         |
| amera | ation |                          |             | istorical |
| name  |       |                          |             | photos?   |
+-------+-------+--------------------------+-------------+-----------+
| Tower | N     | [                        | Axis 200+   | Yes: ARM  |
| cam   | SA-C1 | ftp://ftp.arm.gov/pub/ww | (to be      | data      |
| era - |       | w/incoming](ftp://ftp.ar | replaced    | archive   |
| B     |       | m.gov/pub/www/incoming/) | with 2120)  | under     |
| arrow |       | /nsacam/brw_tower.jpg    |             | "Catalog  |
|       |       |                          |             | Data",    |
|       |       |                          |             | "NSA",    |
|       |       |                          |             | "Surface  |
|       |       |                          |             | Met       |
|       |       |                          |             | eorology" |
+-------+-------+--------------------------+-------------+-----------+
| Sk    | N     | [ftp://ftp.arm.gov       | Axis 200+   | No        |
| ydeck | SA-C1 | /pub/www/incoming](ftp:/ | (to be      |           |
| c     |       | /ftp.arm.gov/pub/www/inc | replaced    |           |
| amera |       | oming/nsacam/barrow.jpg) | with Axis   |           |
| --    |       |                          | 2120)       |           |
| B     |       | [/                       |             |           |
| arrow |       | nsacam/barrow.jpg](ftp:/ |             |           |
|       |       | /ftp.arm.gov/pub/www/inc |             |           |
|       |       | oming/nsacam/barrow.jpg) |             |           |
+-------+-------+--------------------------+-------------+-----------+
| Tower | N     | [ftp://ftp.              | Axis 200+   | No        |
| (pi   | SA-C2 | arm.gov/pub/www/incoming | (to be      |           |
| ling) |       | /nsacam/                 | replaced    |           |
| c     |       | atq_tower.jpg](ftp://ftp | with Axis   |           |
| amera |       | .arm.gov/pub/www/incomin | 2120)       |           |
| --    |       | g /nsacam/atq_tower.jpg) |             |           |
| At    |       |                          |             |           |
| qasuk |       |                          |             |           |
+-------+-------+--------------------------+-------------+-----------+

# Near-Real-Time Data Plots

Real-time data plots from the tower camera are available online at the
following URLs:

-   <ftp://ftp.arm.gov/pub/www/incoming/nsacam/barrow.jpg>

-   <ftp://ftp.arm.gov/pub/www/incoming/nsacam/brw_tower.jpg>

-   <ftp://ftp.arm.gov/pub/www/incoming/nsacam/atq_tower.jpg>.

# Data Description and Examples

## Data File Contents

One data stream, twrcam40m.a1, is produced using the tower camera in
Barrow. The hourly images (in jpg format) from a single day are
compressed into a tar folder. For example, the file
nsatwrcam40mC1.a1.20040701.000000.jpg.tar, when untarred, contains the
hourly jpeg images from the (40-meter) Barrow tower for July 1, 2004.
There are no variables in the data files. The time stamp is in Universal
Time (UT or GMT).

### Primary Variables and Expected Uncertainty

This section is not applicable to this instrument.

#### Definition of Uncertainty

This section is not applicable to this instrument.

### Secondary/Underlying Variables

The following variables can be deduced using the Barrow tower camera
images:

• Visual record of sky conditions on southerly direction

• Fractional snow cover

### Diagnostic Variables

This section is not applicable to this instrument.

### Data Quality Flags

This section is not applicable to this instrument.

### Dimension Variables

This section is not applicable to this instrument.

## Annotated Examples

Below are examples from the two cameras installed in Barrow and one in
Atqasuk.

![](media/image1.jpeg){width="2.9291666666666667in"
height="2.3965277777777776in"}

Figure 1. Image from Barrow skydeck camera. Visible is the instrument
deck in Barrow, as well as conditions on the ground (complete snow
cover), and general weather (partly overcast skies). Only current images
are available from this camera.

![](media/image2.png){width="2.9180555555555556in" height="2.3875in"}
![](media/image3.jpeg){width="2.9180555555555556in" height="2.3875in"}

Figure 2. Winter (Jan 28, 2005) and summer (July 12, 2004) images from
the tower camera located at the top of the 40-meter meteorological tower
in Barrow. Near the upper center of the image, the Barrow instrument
site is visible next to the gravel road. Near the bottom of the summer
image, there are cables visible that are running along the ground to a
5-meter tip tower, on which the downward-looking radiometer instruments
are located. In the winter image only the base of the tip tower is
visible, but not the cables. These images can be used to estimate ground
snow cover, as well as the general weather. The images from this camera
are available from the Atmospheric Radiation Measurement (ARM) Program's
data archive in addition to the current view obtainable from the web.

![](media/image4.png){width="2.9180555555555556in" height="2.3875in"}

Figure 3. Image from Atqasuk cam. In the center is the Atqasuk 5-meter
tip tower, on which meteorological instruments are located as well as
downward-looking radiometers. Behind the tower, on the horizon, is the
Atqasuk instrument shelter, and Atqasuk village lights to the left of
it. The image may be used to estimate snow cover and general weather
conditions. Only current images are available.

## User Notes and Known Problems

The cameras record only ambient light. In winter, the only images that
are not completely dark will be those obtained near solar noon,
approximately 22 UT.

## Frequently Asked Questions

This section is not applicable to this instrument.

# Data Quality

## Data Quality Health and Status

This section is not applicable to this instrument.

## Data Reviews by Instrument Mentor

This section is not applicable to this instrument.

## Data Assessments by Site Scientist/Data Quality Office

This section is not applicable to this instrument.

## Value-Added Procedures and Quality Measurement Experiments

This section is not applicable to this instrument.

# Instrument Details

## Detailed Description

### List of Components

From the axis website:

  ---------------------- ----------------------------------------------------- -----------------------------------------------------
                         ![](media/image5.jpeg){width="0.8854166666666666in"   ![](media/image6.jpeg){width="0.6979166666666666in"
                         height="0.625in"}                                     height="0.625in"}

  **Embedded\            [AXIS                                                 [AXIS
  camera**               2120](http://axis.com/products/cam_2120/index.htm)    2420](http://axis.com/products/cam_2420/index.htm) \*

  **Compression**        ![](media/image7.png){width="0.10416666666666667in"   ![](media/image7.png){width="0.10416666666666667in"
                         height="0.10416666666666667in"}                       height="0.10416666666666667in"}

  **Frames per\          Motion JPEG                                           Motion JPEG
  second**                                                                     

  **Indoor/outdoor use** Up to 30/25\                                          Up to 30/25\
                         (NTSC/PAL)                                            (NTSC/PAL)

  **Audio support**      ![](media/image7.png){width="0.10416666666666667in"   ![](media/image7.png){width="0.10416666666666667in"
                         height="0.10416666666666667in"}\*\*                   height="0.10416666666666667in"}\*\*

  **Motion detection**   ![](media/image7.png){width="0.10416666666666667in"   ![](media/image7.png){width="0.10416666666666667in"
                         height="0.10416666666666667in"}**\*\*\***             height="0.10416666666666667in"}**\*\*\***

  **Pan/Tilt/Zoom\       ![](media/image7.png){width="0.10416666666666667in"   ![](media/image7.png){width="0.10416666666666667in"
  control**              height="0.10416666666666667in"}                       height="0.10416666666666667in"}

  **Max video\                                                                 ![](media/image7.png){width="0.10416666666666667in"
  resolution**                                                                 height="0.10416666666666667in"}\*\*\*\*

  **Image sensor**       704x576 (PAL)\                                        704x576 (PAL)\
                         704x480 (NTSC)                                        704x480 (NTSC)

  **Zoom**               1/3\'\' Sony ExView HAD interlaced CCD                1/3\'\' Sony ExView HAD interlaced CCD

  **Lens type**          Manual                                                Manual with support for external control

  **Lens changeable**    Varifocal\                                            Varifocal (2.8-12 mm)\
                         (3.5-8.0 mm), DC-iris lens, CS-Mount                  CS-Mount, auto iris lens

  **Min. illumination    ![](media/image7.png){width="0.10416666666666667in"   ![](media/image7.png){width="0.10416666666666667in"
  Light sensitivity**    height="0.10416666666666667in"}                       height="0.10416666666666667in"}

  **Analog output**      1 lux                                                 0.5 lux \*\*\*\*\*

  **Ethernet networks**                                                        ![](media/image7.png){width="0.10416666666666667in"
                                                                               height="0.10416666666666667in"}

  **Modem support**      10/100BaseT                                           10/100BaseT

  **Serial\              ![](media/image7.png){width="0.10416666666666667in"   ![](media/image7.png){width="0.10416666666666667in"
  connectors**           height="0.10416666666666667in"}                       height="0.10416666666666667in"}

  **Alarm input\         RS232                                                 RS232, RS422, RS485
  relay output**                                                               

  **Other features**     ![](media/image7.png){width="0.10416666666666667in"   ![](media/image7.png){width="0.10416666666666667in"
                         height="0.10416666666666667in"}                       height="0.10416666666666667in"}
  ---------------------- ----------------------------------------------------- -----------------------------------------------------

The Axis 200+ cameras will soon be removed from usage on the NSA site.
The overview of 200+ from the axis website is as follows:

Direct digital camera, 24-bit color

Charge-coupled device (CCD): High-quality 1/3\", 768 x 582 pixels

Lens mount: CS mount (C mount with C/CS ring)

Lens iris: Auto iris lenses supported

Illumination range: 5 - 5000 Lux (with delivered lens), 2 - 200.000 Lux
(with F1.0 auto iris lens)

White balance: Automatic or fixed.

Gamma: 0.45

Optical filter: Quartz low-pass filter with infrared (IR) cut filtering.

Delivered with a basic wide angle lens. Focus can be adjusted from 0.02
in (0.5 mm) to infinity. The lens can be replaced with any
industry-standard C or CS lens.

Focal length: 5.5 mm

Apperture: Fixed F2.0

Thread: M12P0.5 mm

Angle of view: Approx. 51 deg. horizontal, 39 deg. vertical

Axis 2120 description from the axis website:

Camera

• Digital, 24-bit color

Image sensor

• 1/3-inch Sony super HAD interlaced CCD.

• HxV: 768x495 (NTSC),.

• Resolution (pixels): 704x480 (NTSC)

Exposure

• Backlight compensation

• Automatic Gain Control (AGC)

• Automatic and fixed White Balance

• Electronic shutter: 1/60s -1/10.000 sec. NTSC

Sensitivity

• Illumination range: 1 -- 200,000 Lux with F1.0 DC-Iris lens. About 1
to 5,000 Lux with fixed iris lens.

Lens

• Standard CS mount lens fitting

• DC-Iris vari-focal (zoom) lens 3.5--8.0mm eqv. to 25-55mm on a 35mm
camera

Image

• Image frame rate: up to 30 frames/s at 352x240 resolution. Up to 12
frames/s at 704x480 resolution.

• JPEG still images and Motion-JPEG video

Axis 2420 description from the axis website:

Camera

• Digital, 24-bit color

Image sensor

• 1/3-inch Sony super HAD interlaced CCD

• HxV: 768x495 (NTSC)

• Resolution (pixels): 704x480 (NTSC)

• Horizontal resolution: 480 TV lines

Exposure

• Backlight Compensation

• AGC

• Automatic and fixed White Balance

• Electronic shutter:

1/60 - 1/10.000 sec. (NTSC)

Sensitivity

• Illumination range: 1 to 200 000 Lux with F1.0 DC-Iris lens. Excellent
in low light situations.

Video Output

• 1.0V (p-p) 75 ohm, sync negative

Signal-to-Noise Ratio

• 50dB (AGC off).

The cameras are at present housed in Pelco (pelco.com) enclosures, model
number EH4718-1, with a window defroster HK47-1.

### System Configuration and Measurement Methods

This section is not applicable to this instrument.

### Specifications

This section is not applicable to this instrument.

## Theory of Operation

This section is not applicable to this instrument.

## Calibration

### Theory

This section is not applicable to this instrument.

### Procedures

This section is not applicable to this instrument.

### History

This section is not applicable to this instrument.

## Operation and Maintenance

### User Manual

This section is not applicable to this instrument.

### Routine and Corrective Maintenance Documentation

This section is not applicable to this instrument.

### Software Documentation

This section is not applicable to this instrument.

### Additional Documentation

This section is not applicable to this instrument.

## Glossary

See the [ARM Glossary](http://www.arm.gov/about/glossary.stm).

## Acronyms

AGC Automatic Gain Control

ARM Atmospheric Radiation Measurement (Program)

CCD charge-coupled device

DC direct current

GMT Greenwich Mean Time

IR infrared

UT Universal Time

See the [ARM Acronyms and
Abbreviations](http://www.arm.gov/about/acronyms.stm).

## Citable References

This section is not applicable to this instrument.