NIDS Format
Nexrad Level 3 Data Format
NIDS data is a format for displaying Nexrad data. NIDS data is separated into the
following blocks:
Tables:
| Halfword |
Name |
Description |
| 01 |
Message Code |
See message code table below |
| 02 |
Date of Message |
Number of days since 1 Jan 1970 |
| 03 |
Time of Message (MSW) |
Number of seconds since midnight |
| 04 |
Time (LSW) |
|
| 05 |
Length of Message (MSW) |
Number of bytes in message including header |
| 06 |
Length (LSW) |
|
| 07 |
Source ID |
|
| 08 |
Destination ID |
|
| 09 |
Number of Blocks |
1 (Header Block) + number of blocks in message |
| Halfword |
Name |
Description |
| 10 |
Divider |
Integer value -1 |
| 11 |
Latitude of Radar (MSW) |
Latitude*1000, + is north |
| 12 |
Latitude (LSW) |
|
| 13 |
Longitude of Radar (MSW) |
Longitude*1000, + is east |
| 14 |
Longitude (LSW) |
|
| 15 |
Height of Radar |
Feet above sea level |
| 16 |
Product Code |
See message code table below |
| 17 |
Operational Mode |
0=Maintenance, 1=Clear air, 2=Precipitation/Severe weather |
| 18 |
Volume Scan Pattern |
RDA volume coverage pattern |
| 19 |
Sequence Number |
Sequence number of the request that generated the product |
| 20 |
Volume Scan Number |
Counter, cycles 1 to 80 |
| 21 |
Volume Scan Date |
|
| 22 |
Volume Scan Time (MSW) |
|
| 23 |
Time (LSW) |
|
| 24 |
Product Generation Date |
|
| 25 |
Product Generation Time (MSW) |
|
| 26 |
Time (LSW) |
|
| 27 |
P1 |
Product specific codes, see product codes below |
| 28 |
P2 |
|
| 29 |
Elevation Number |
Elevation scan within volume scan |
| 30 |
P3 |
|
| 31 |
Data 1 Threshold |
Data threshold values, see threshold discussion below |
| 32 |
Data 2 Threshold |
|
| 33 |
Data 3 Threshold |
|
| 34 |
Data 4 Threshold |
|
| 35 |
Data 5 Threshold |
|
| 36 |
Data 6 Threshold |
|
| 37 |
Data 7 Threshold |
|
| 38 |
Data 8 Threshold |
|
| 39 |
Data 9 Threshold |
|
| 40 |
Data 10 Threshold |
|
| 41 |
Data 11 Threshold |
|
| 42 |
Data 12 Threshold |
|
| 43 |
Data 13 Threshold |
|
| 44 |
Data 14 Threshold |
|
| 45 |
Data 15 Threshold |
|
| 46 |
Data 16 Threshold |
|
| 47 |
P4 |
|
| 48 |
P5 |
|
| 49 |
P6 |
|
| 50 |
P7 |
|
| 51 |
P8 |
|
| 52 |
P9 |
|
| 53 |
P10 |
|
| 54 |
Number of Maps |
|
| 55 |
Offset to Symbology Block (MSW) |
Number of halfwords (2 bytes) from start of product to block |
| 56 |
Offset (LSW) |
|
| 57 |
Offset to Graphic Block (MSW) |
|
| 58 |
Offset (LSW) |
|
| 59 |
Offset to Tabular Block (MSW) |
|
| 60 |
Offset (LSW) |
|
The Symbology Block has a header plus a number of data layers. These layers can
be graphical such as radial and rastor scan data or could be textual or symbolic such as
TVS locations.
| Halfword |
Name |
Description |
| 01 |
Divider |
|
| 02 |
Block ID |
Integer value 1 |
| 03 |
Length of Block (MSW) |
Length in bytes |
| 04 |
Length (LSW) |
|
| 05 |
Number of Layers |
|
Within the layer, there are a number of data packets which describe the type of
information to be plotted.
| Halfword |
Name |
Description |
| 01 |
Divider |
|
| 02 |
Length of Block (MSW) |
Length in bytes |
| 03 |
Length (LSW) |
|
| 04-## |
Display Data Packets |
|
Radial data contains values for each bin within a particular radial. Each radial
is defined by a start and end angle and by distance. There are multiple radials that
define a full scan.
| Halfword |
Name |
Description |
| 01 |
Packet Code |
Hex "AF1F" |
| 02 |
Index of First Range Bin |
|
| 03 |
Number of Range Bins |
Number of bins in each radial |
| 04 |
I Center of Sweep |
Center point location in a -2048 to 2047 coordinate region(mostly 0,0) |
| 05 |
J Center of Sweep |
|
| 06 |
Scale Factor |
Number of pixels per range bin |
| 07 |
Number of Radials |
|
Individual Radials
Each radial contains Run Length Encoded (RLE) values.
| Halfword |
Name |
Description |
| 01 |
Number of RLE Halfwords |
RLE data always padded to even halfword boundary |
| 02 |
Radial Start Angle |
Angle*10, scan direction is always clockwise |
| 03 |
Radial Angle Delta |
Angle*10 |
| 04 |
Run0 |
Code0 |
Run1 |
Code1 |
Run is 4 bit value for number of bins for this value |
| 05 |
Run2 |
Code2 |
Run3 |
Code3 |
Code is 4 bit value (0-15) for the value within the run |
| 06-## |
Run Codes |
Repeated for entire radial |
| ## |
RunN |
CodeN |
00 |
00 |
|
Raster data is pixelized data defined by rows and columns.
| Halfword |
Name |
Description |
| 01 |
Packet Code |
Hex "BA0F" or "BA07" |
| 02 |
Op Flags |
Hex "8000" |
| 03 |
Op Flags |
Hex "00C0" |
| 04 |
I Start Coordinate |
Start coordinate on -2048 to 2047 coordinate system |
| 05 |
J Start Coordinate |
|
| 06 |
X Scale (INT) |
Reserved |
| 07 |
X Scale (FRACT) |
|
| 08 |
Y Scale (INT) |
Reserved |
| 09 |
Y Scale (FRACT) |
|
| 10 |
Number of Rows |
|
| 11 |
Packing Descriptor |
Always 2 |
Individual Rows
Each row contains Run Length Encoded (RLE) values.
| Halfword |
Name |
Description |
| 01 |
Number of Bytes in Row |
RLE data always padded to even halfword boundary |
| 02 |
Run0 |
Code0 |
Run1 |
Code1 |
Run is 4 bit value for number of bins for this value |
| 03 |
Run2 |
Code2 |
Run3 |
Code3 |
Code is 4 bit value (0-15) for the value within the run |
| 04-## |
Run Codes |
Repeated for entire row |
| ## |
RunN |
CodeN |
00 |
00 |
|
These define the location and size of vector arrows to be plotted.
| Halfword |
Name |
Description |
| 01 |
Packet Code = 5 |
Hex "5" |
| 02 |
Length of Data |
In bytes |
Individual Vectors
Each arrow is 5 halfwords and is repeated until byte length.
| 01 |
I Coordinate |
|
| 02 |
J Coordinate |
|
| 03 |
Direction of Arrow |
In degrees |
| 04 |
Arrow Length |
In pixels |
| 05 |
Arrow Head Length |
In pixels |
These define the location and size of wind barbs to be plotted.
| Halfword |
Name |
Description |
| 01 |
Packet Code = 4 |
Hex "4" |
| 02 |
Length of Data |
In bytes |
Individual Barbs
Each barb is 5 halfwords and is repeated until byte length.
| Halfword |
Name |
Description |
| 01 |
Value |
Color value (0-5) representing RMS variation of wind speed |
| 02 |
I Coordinate |
|
| 03 |
J Coordinate |
|
| 04 |
Direction of Wind |
In degrees |
| 05 |
Wind Speed |
|
| Halfword |
Name |
Description |
| 01 |
Packet Code = 17 |
Hex "11" |
| 02 |
Op Flags |
Reserved |
| 03 |
Op Flags |
Reserved |
| 04 |
Number of LFM Boxes in Row |
|
| 05 |
Number of Rows |
|
Individual Rows
Each row contains Run Length Encoded (RLE) values.
| Halfword |
Name |
Description |
| 01 |
Number of Bytes in Row |
RLE data always padded to even halfword boundary |
| 02 |
Run0 |
Code0 |
Run is 8 bit value for number of bins for this value |
| 03 |
Run1 |
Code1 |
Code is 8 bit value (0-255) for the value within the run |
| 04-## |
Run Codes |
Repeated for entire row |
| ## |
RunN |
CodeN |
|
This is a set of unlinked vectors that plot disconnected lines on the plot.
| Halfword |
Name |
Description |
| 01 |
Packet Code = 7 |
Hex "7" |
| 02 |
Length of Data |
In bytes |
| 03 |
Vector 1, I Start |
Vector 1 start and end coordinates |
| 04 |
Vector 1, J Start |
|
| 05 |
Vector 1, I End |
|
| 06 |
Vector 1, J End |
|
| 07 |
Vector 2, I Start |
Vector 2 start and end coordinates |
| 08 |
Vector 2, J Start |
|
| 09 |
Vector 2, I End |
|
| 10 |
Vector 2, J End |
|
| 11-## |
Repeated Vectors |
|
This is a set of unlinked vectors that plot disconnected lines on the plot. This
contains a value level for coloring.
| Halfword |
Name |
Description |
| 01 |
Packet Code = 7 |
Hex "7" |
| 02 |
Length of Data |
In bytes |
| 03 |
Value |
Color level of vector |
| 04 |
Vector 1, I Start |
Vector 1 start and end coordinates |
| 05 |
Vector 1, J Start |
|
| 06 |
Vector 1, I End |
|
| 07 |
Vector 1, J End |
|
| 08 |
Vector 2, I Start |
Vector 2 start and end coordinates |
| 09 |
Vector 2, J Start |
|
| 10 |
Vector 2, I End |
|
| 11 |
Vector 2, J End |
|
| 12-## |
Repeated Vectors |
|
This is for plotting text and symbols.
| Halfword |
Name |
Description |
| 01 |
Packet Code = 1 |
Hex "1" |
| 02 |
Length of Data |
In bytes |
| 03 |
I Start |
Vector 1 start and end coordinates |
| 04 |
J Start |
|
| 05 |
Char1 |
Char2 |
Each character in string |
| 06 |
Char3 |
Char4 |
|
| 07-## |
Repeated |
|
| ## |
CharN-1 |
CharN |
|
This is for plotting text and symbols. A color value is also listed
| Halfword |
Name |
Description |
| 01 |
Packet Code = 1 |
Hex "1" |
| 02 |
Length of Data |
In bytes |
| 03 |
Value of String |
|
| 04 |
I Start |
Vector 1 start and end coordinates |
| 05 |
J Start |
|
| 06 |
Char1 |
Char2 |
Each character in string |
| 07 |
Char3 |
Char4 |
|
| 08-## |
Repeated |
|
| ## |
CharN-1 |
CharN |
|
| Code |
Name |
Resolution |
Range |
Levels |
Description |
| 2 |
GSM - General Status Message |
NA |
NA |
NA |
Text |
| 5 |
FTM - Free Text Message |
NA |
NA |
NA |
Text |
| 16 |
Base Reflectivity |
.54nm x 1deg |
124 |
8 |
Radial Image |
| 17 |
Base Reflectivity |
1.1nm x 1deg |
248 |
8 |
Radial Image |
| 18 |
Base Reflectivity |
2.2nm x 1deg |
248 |
8 |
Radial Image |
| 19 |
N#R - Base Reflectivity |
.54nm x 1deg |
124 |
16 |
Radial Image |
| 20 |
N0Z - Base Reflectivity |
1.1nm x 1deg |
248 |
16 |
Radial Image |
| 21 |
Base Reflectivity |
2.2nm x 1deg |
248 |
16 |
Radial Image |
| 22 |
Base Velocity |
.13nm x 1deg |
32 |
8 |
Radial Image |
| 23 |
Base Velocity |
.27nm x 1deg |
62 |
8 |
Radial Image |
| 24 |
Base Velocity |
.54nm x 1deg |
124 |
8 |
Radial Image |
| 25 |
N0W - Base Velocity |
.13nm x 1deg |
32 |
16 |
Radial Image |
| 26 |
Base Velocity |
.27nm x 1deg |
62 |
16 |
Radial Image |
| 27 |
N#V - Base Velocity |
.54nm x 1deg |
124 |
16 |
Radial Image |
| 28 |
NSP - Base Spectrum Width |
.13nm x 1deg |
32 |
8 |
Radial Image |
| 29 |
Base Spectrum Width |
.27nm x 1deg |
62 |
8 |
Radial Image |
| 30 |
NSW - Base Spectrum Width |
.54nm x 1deg |
124 |
8 |
Radial Image |
| 32 |
DHR - Dgitial Hybrid Reflectivity |
.54nm x 1 deg |
124 |
256 |
Radial Image |
| 34 |
NCF - Clutter Filter Control |
.54nm x .54nm |
124 |
|
|
| 35 |
Composite Reflectivity |
.54nm x .54nm |
124 |
8 |
Rastor Image+Alphanumeric Data |
| 36 |
NCO - Composite Reflectivity |
2.2nm x 2.2nm |
248 |
8 |
Rastor Image |
| 37 |
NCR - Composite Reflectivity |
.54nm x .54nm |
124 |
16 |
Rastor Image+Alphanumeric Data |
| 38 |
NCZ - Composite Reflectivity |
2.2nm x 2.2nm |
248 |
16 |
Rastor Image |
| 41 |
NET - Echo Tops |
2.2nm x 2.2nm |
124 |
16 |
Rastor Image |
| 47 |
NWP - Severe Weather Probability |
.54nmx1deg |
124 |
|
|
| 48 |
NVW - VAD Wind Profile |
5knots |
NA |
5 |
Alphanumeric+Wind Barbs |
| 55 |
Storm Relative Mean Radial Velocity |
.27nm x 1deg |
27 |
16 |
Radial Image (Region) |
| 56 |
N#S - Storm Relative Mean Radial Velocity |
.54nm x 1deg |
124 |
16 |
Radial Image (Map) |
| 57 |
NVL - Vertically Integrated Liquid |
2.2nm x 2.2nm |
124 |
16 |
Rastor Image |
| 58 |
NST - Storm Tracking Info |
|
186 |
|
|
| 59 |
NHI - Hail Index |
|
124 |
|
|
| 60 |
NME - Mesocyclone |
|
124 |
|
|
| 61 |
NTV - Tornado Vortex Signature |
|
124 |
|
|
| 62 |
NSS - Storm Structure |
|
248 |
|
|
| 63 |
Layer Composite Reflectivity |
2.2nm x 2.2nm |
124 |
8 |
Rastor Image (Layer 1 average) |
| 64 |
Layer Composite Reflectivity |
2.2nm x 2.2nm |
124 |
8 |
Rastor Image (Layer 2 average) |
| 65 |
NLL - Layer Composite Reflectivity |
2.2nm x 2.2nm |
124 |
8 |
Rastor Image (Layer 1 maximum) |
| 66 |
NML - Layer Composite Reflectivity |
2.2nm x 2.2nm |
124 |
8 |
Rastor Image (Layer 1 maximum) |
| 74 |
RCM - Radar Coded Message |
|
|
|
|
| 78 |
N1P - Surface Rainfall Accumulation - 1hr |
1.1nm x 1.1nm |
124 |
16 |
Rastor Image |
| 79 |
N3P - Surface Rainfall Accumulation - 3hr |
1.1nm x 1.1nm |
124 |
16 |
Rastor Image |
| 80 |
NTP - Storm Total Rainfall Accumulation |
1.1nm x 1.1nm |
124 |
16 |
Rastor Image |
| 81 |
DPA - Hourly Digital Precipitation Array |
1/40 LFM |
124 |
100max |
Rastor Image on LFM grid |
| 82 |
SPD - Supplemental Data |
|
|
|
|
| 89 |
Layer Composite Reflectivity |
2.2nm x 2.2nm |
124 |
8 |
Rastor Image (Layer 3 average) |
| 94 |
N0Q - Base Reflectivity |
.54nm x 1 deg |
248 |
256 |
Radial Image |
| 99 |
N0U - Base Velocity |
.13nm x 1 deg |
248 |
256 |
Radial Image |
| 134 |
DVL - Digital Vert Int Liquid |
.54 x 1deg |
248 |
256 |
Radial Image |
| 135 |
EET - Enhanced Echo Tops |
.54nm x 1deg |
186 |
256 |
Radial Image |
| 138 |
DSP - Digital Storm Total Precipitation |
.54nm x 1deg |
124 |
256 |
Radial Image |
| 141 |
NMD - Digital Mesocyclone Detection Algorithm |
|
124 |
|
|
| 152 |
RSL - Radar Status Log |
|
124 |
|
|
| 153 |
N#B - Hi-res Base Reflectivity |
.13nm x .5deg |
248 |
256 |
Radial Image |
| 154 |
N#G - Hi-res Base Velocity |
.13nm x .5deg |
124 |
256 |
Radial Image |
| 159 |
N#X - Differential Reflectivity |
|
162 |
|
Radial Image |
| 161 |
N#C - Correlation Coefficient |
|
162 |
|
Radial Image |
| 163 |
N#K - Specific Differential Phase |
|
162 |
|
Radial Image |
| 165 |
N#H - Hydrometeor Classification |
|
162 |
|
Radial Image |
| 166 |
Melting Layer |
|
|
|
|
| 169 |
OHA - Sruface One Hour Accumulation |
1.1nm x 1deg |
124 |
16 |
Radial Image |
| 170 |
DAA - Hourly Digital Accumulation Array |
.25nm x 1 deg |
124 |
255 |
Radial Image |
| 171 |
PTA - Storm Total Accumulation |
|
124 |
|
|
| 172 |
DTA - Digital Storm Total Accumulation |
.25nm x 1deg |
124 |
256 |
Radial Image |
| 173 |
DU3 - Surface Rainfall Accumulation (3-hr) |
|
124 |
|
|
| 175 |
DSD - Storm Total Precipitation Difference |
|
124 |
|
|
| 176 |
DPR - Instantaneous Precipitation Rate |
|
124 |
|
|
| 177 |
HHC - Hybrid Hydrometeor Classification |
|
124 |
|
|
| 180 |
TR# - TDWR Base Reflectivity |
|
48 |
|
|
| 181 |
TR# - TDWR Base Reflectivity |
|
48 |
|
|
| 182 |
TV# - TDWR Base Velocity |
|
48 |
|
|
| 186 |
TZ# - TDWR Long Range Base Reflectivity |
|
225 |
|
|
| Product Name |
P3 (HW#30) |
P4 (HW#47) |
P5 (HW#48) |
P6 (HW#49) |
| Base Reflectivity |
Elevation Angle*10 |
Maximum Reflectivity |
|
|
| Base Velocity |
Elevation Angle*10 |
Max Negative Velocity |
Max Positive Velocity |
|
| Base Spectrum Width |
Elevation Angle*10 |
Maximum Width |
|
|
| Composite Reflectivity |
|
Maximum Reflectivity |
|
|
| Echo Tops |
|
Maximum Top |
|
|
| Hourly Digital Precipitation |
|
Max Rainfall Accumulation |
|
|
| Layer Composite Reflectivity |
|
Maximum Reflectivity |
Bottom of Layer (1000ft) |
Top of Layer |
| Storm Rel Mn Velocity |
Elevation Angle*10 |
Max Negative Velocity |
Max Positive Velocity |
|
| Surface Rainfall Accumulation |
|
Max Rainfall Accumulation |
|
|
| Storm Total Rainfall |
|
Max Rainfall Accumulation |
Begin Julian Date (day) |
Begin Time (min) |
| Vertically Integrated Liquid |
|
Max VIL |
|
|
| Product Name |
P7 (HW#50) |
P8 (HW#51) |
P9 (HW#52) |
P10 (HW#53) |
| Storm Total Rainfall |
End Julian Date (day) |
End Time (min) |
|
|