Draw2D V1.1 JavaScript Graphics Engine Update Released

Version 1.1 of the Draw2D JavaScript Graphics Engine has been released. This is a minor update that adds speed improvements to all the curve drawing classes (Quadradic Curves, Cubic Curves, Round Rectangles, Ovals And Arcs) and fixes a bug in the rendering of Cubic Curves.

You can get the source code, several example HTML pages, and a Programmer's Manual here.

The code has been placed in the public domain.

Previous Posts In This Series
Draw2D JavaScript Graphics Engine Released

Draw2D JavaScript Graphics Engine Released

Draw2D version 1.0 has just been released and you can get it here.

Draw2D is a JavaScript graphics engine that allows you to add dynamically created shapes to any web page. Draw2D also supports mouse events, allowing shapes to respond to user input. Like all my coding projects, the Draw2D code has been placed in the public domain.

Draw2D will serve as the graphics engine for new features available in the Climate Scientist Starter Kit, Version 2.0. More details on this will be given in future posts.

The download includes source code, several HTML example pages, and a programmer's guide in Apple Pages, Microsoft Word, and Adobe PDF formats.

I'll finish out this post with a few screen shots showing what Draw2D can do.

Points, Lines, Quadradic Curves, Cubic Curves




Triangles And Polygons


Rectangles And Round Rectangles


Ovals And Arcs

NSIDC L2_Land Source Code Walkthrough

In this post we're going to take a closer look at the NSIDC source code that produces their Level 2B Land product. For a very brief overview of the Level 2B Land and other NSDIC source see this post.

Inputs
The source code uses the Level 2A Brightness Temperature file as well as several data files as input. The data files are stored in the anc folder that comes with the source.

NOTE: The data files in the anc folder are binary files, so if you want to see what data they contain, you'll need to write a translation program to convert them to ASCII text. See the the Fortran file ancdata.blk in the src/land/level2/common folder for a description of the data in each data file.

Source Code
The source code is located in the src/land/level2 folder. There are three main groups of source code: C code, Fortran code and common code located in the common folder. The C code is used mainly for QA and I/O purposes. It's the Fortran code that does the real work. The code in the common folder is also Fortran code, stored as reusable blocks.

NOTE: Recall from this post that the AMSR-E scans detects both the H and V polarization of light. The H and V values are what allows the source code to detect land, rain, wind, and other characteristics. It's the source code that actually detects these characteristics, not the satellite.

NOTE: You'll see the term TB used throughout the code. This is shorthand for Brightness Temperature.

The main file is amsre_l2main.f. This file will call all the other code as needed. Overall, the program performs the following processes:

1. Ingest ancillary databases and external parameters.
2. Ingest AMSR-E Level 2A TB data.
3. Grid TB data on EASE-grid projection.
4. Export gridded TB data.
5. Perform geophysical retrieval.
6. Export results/flags as Level 2B land product.

Other source files of note are:

• dobsonv3.f  Compute the dielectric constant of soil as a function of frequency, soil moisture, sand/clay fractions, and surface temperature.
• fmod_pr3ch.f Compute TB as a function of the 6.9, 10.7, and 18.7 frequencies.
• fmod_regrs.f Compute vegetation water content and soil moisture as a function of the 10.7, and 18.7 frequencies.
• fmod_tb4ch.f Compute R squared and Chi values based on the 10.7, and 18.7 frequencies and values calculated in dobsonv3.f.
• fmod_tb6ch.f Compute R squared and Chi values based on the 6.9, 10.7, and 18.7 frequencies and values calculated in dobsonv3.f.

Execution

AMSRE_L2MAIN() executes with 5 command-line arguments:

                  amsre_l2main.exe INPUT_L2A ANCIL_DIR L2B_DIR GTB_DIR PMC_VER

                INPUT_L2A: Filename of the input Level 2A data file

                ANCIL_DIR: Directory of ancillary databases

                L2B_DIR:   Directory of output Level 2B data files

                GTB_DIR:   Directory of gridded TB data files

                PMC_VER:   Product maturity code and PGE version number

NOTE: This program is designed to execute on big endian machines. If you're using a little endian machine (Intel machines are little endian) you'll need to add code that converts binary data to little endian values. You'll want to change the file l2ard.c and any code that loads ancillary data larger than than one byte. C++ code for swapping bytes is provided here:


inline bool is_bigendian()
{
const int i = 1;
bool bReturn = ( (*(char*)&i) == 0 );
return bReturn;
} // is_bigendian

inline char* reverse_16_bit (char* in16Bit)
{
char aReversed16Bit[2];

aReversed16Bit[0] = in16Bit[1];
aReversed16Bit[1] = in16Bit[0];
in16Bit[0] = aReversed16Bit[0];
in16Bit[1] = aReversed16Bit[1];

return in16Bit;
} // reverse_16_bit

inline char* reverse_16_bit_if_little_endian (char* in16Bit)
{
if (false == is_bigendian())
return reverse_16_bit(in16Bit);
return in16Bit;
} // reverse_16_bit_if_little_endian

inline char* reverse_32_bit(char* in32Bit)
{
char aReversed32Bit[4];

aReversed32Bit[0] = in32Bit[3];
aReversed32Bit[1] = in32Bit[2];
aReversed32Bit[2] = in32Bit[1];
aReversed32Bit[3] = in32Bit[0];
in32Bit[0] = aReversed32Bit[0];
in32Bit[1] = aReversed32Bit[1];
in32Bit[2] = aReversed32Bit[2];
in32Bit[3] = aReversed32Bit[3];

return in32Bit;
} // reverse_32_bit

inline char* reverse_32_bit_if_little_endian (char* in32Bit)
{
if (false == is_bigendian())
return reverse_32_bit(in32Bit);
return in32Bit;
} // reverse_32_bit_if_little_endian

inline char* reverse_64_bit(char* in64Bit)
{
char aReversed64Bit[8];

aReversed64Bit[0] = in64Bit[7];
aReversed64Bit[1] = in64Bit[6];
aReversed64Bit[2] = in64Bit[5];
aReversed64Bit[3] = in64Bit[4];
aReversed16Bit[4] = in64Bit[3];
aReversed64Bit[5] = in64Bit[2];
aReversed64Bit[6] = in64Bit[1];
aReversed64Bit[7] = in64Bit[0];
in64Bit[0] = aReversed64Bit[0];
in64Bit[1] = aReversed64Bit[1];
in64Bit[2] = aReversed64Bit[2];
in64Bit[3] = aReversed64Bit[3];
in64Bit[4] = aReversed64Bit[4];
in64Bit[5] = aReversed64Bit[5];
in64Bit[6] = aReversed64Bit[6];
in64Bit[7] = aReversed64Bit[7];

return in64Bit;
} // reverse_64_bit

inline char* reverse_64_bit_if_little_endian (char* in64Bit)
{
if (false == is_bigendian())
return reverse_32_bit(in64Bit);
return in64Bit;
} // reverse_64_bit_if_little_endian


template<class NUMBER_TYPE>
inline NUMBER_TYPE reverse_bytes(NUMBER_TYPE inValue)
{
if (2 == sizeof(inValue))
return *(reverse_16_bit((char*) &inValue));
if (4 == sizeof(inValue))
return *(reverse_32_bit((char*) &inValue));
if (8 == sizeof(inValue))
return *(reverse_64_bit((char*) &inValue));
return inValue;
} // reverse_bytes

template<class NUMBER_TYPE>
inline NUMBER_TYPE reverse_bytes_if_little_endian(NUMBER_TYPE inValue)
{
if (false == is_bigendian())
return reverse_bytes(inValue);
return inValue;
} // reverse_bytes_if_little_endian

Output

The Level 2B land product contains surface type, surface moisture, and vegetation water content information for the Earth.

Additional Information

Useful documentation on the algorithms is available at AMSR-E/Aqua L2B Surface Soil Moisture, Ancillary Parms, & QC EASE-Grids.

References:

First Look At NSIDC Source Code

Taking A Look At Raw AMSR-E Data

AMSR-E/Aqua L2B Surface Soil Moisture, Ancillary Parms, & QC EASE-Grids

First Look At NSIDC Source Code

In this post we'll take a look at how to order source code from the National Snow and Ice Data Center and what that source code does.

Ordering The Source Code
The source code is stored in 9 folders that NSIDC calls Delivered Algorithm Packages (DAPs). You must order the source code before you download it. This is done by sending off a request to their User Services department using this form. Just tell them you'd like to download the DAPs and they will give you instructions on how to register and download the DAPS via FTP.

Some of the DAPS also use the PORT Mathematical Subroutine Library.

The Code
The code you'll get is written in Fortran and C. There are also data files required by each DAP. Each DAP comes in its own folder and each folder contains a zip file of the source and data files, as well as some read-me files. After you unzip the files, you'll find the source code in the src folder and the data files in the anc folder.

To finish out this post, we'll take a quick look at each DAP.

L2_Land

Input File	Level 2A Brightness Temperature File
Output File	Level 2 Land File
Data Produced	Soil Moisture, Vegetation Water Content, Land Surface Temperature, Surface Type
Uses PORT?	Yes
Platform	Linux

L2_Rain

Input File	Level 2A Brightness Temperature File
Output File	Level 2 Rain File
Data Produced	Rain Rate, Rain Type, Rain Status, Surface Type
Uses PORT?	No
Platform	Linux

L2A

Input File	Level 1A AMSR-E File
Output File	Level 2A Brightness Temperature File
Data Produced	AMSR-E Scan Information
Uses PORT?	No
Platform	Windows 2000/XP

L2B_Ocean

Input File	Level 2A Brightness Temperature File
Output File	Level 2B Ocean File
Data Produced	Very Low Resolution Sea Surface Temperature, Low Resolution Sea Surface Temperature, Low Resolution Wind, Medium Resolution Wind, Medium Resolution Vapor, High Resolution Cloud
Uses PORT?	No
Platform	Linux

L3 Land

Input File	30 Days Of Level 2 Land Files
Output File	Level 2B Ocean File
Data Produced	AMSR-E Frequency Scans, Soil Moisture, Vegetation Water Content, Land Surface Temperature
Uses PORT?	No
Platform	Linux

L3 Ocean

Input File	Level 2B Land Files (Days Worth, Weeks Worth, Month's Worth)
Output File	Level 2B Ocean File
Data Produced	Low Resolution Sea Surface Temperature, Low Resolution Wind, Medium Resolution Wind, Medium Resolution Vapor, High Resolution Cloud
Uses PORT?	No
Platform	Linux

L3 Rain

Input File	Level 2A Brightness Temperature File (Month's Worth) Level 2B Rain Files (Month's Worth)
Output File	Level 3 Rain File
Data Produced	Land Rain, Ocean Rain
Uses PORT?	No
Platform	Linux

L3 Sea Ice

Input File	Level 2A Brightness Temperature File (Day's Worth)
Output File	Level 3 Sea Ice File
Data Produced	Frequency Scan Data, Ice Data, Snow Depth Data
Uses PORT?	No
Platform	Linux

L3 Snow

Input File	Level 2A Brightness Temperature File (Day's Worth), Level 3 Snow Files (5 Days Worth, Month's Worth)
Output File	Level 3 Snow File (Daily, 5 Days, Monthly)
Data Produced	Snow Data
Uses PORT?	No
Platform	Linux

References:
National Snow And Ice Data Center User Services Contact Form
PORT Mathematical Subroutine Library

Source Code!

Oh yeah! I have source code from the National Snow And Ice Data Center! URAH!

I've just downloaded it and haven't had the time to go over it yet (there's nine different groups of source). But details will follow.