gis-tools-ts
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A collection of geospatial tools primarily designed for WGS84, Web Mercator, and S2.
394 lines • 18.1 kB
JavaScript
import { grib2LookupTable51, grib2LookupTable54, grib2LookupTable540, grib2LookupTable55, grib2LookupTable56, grib2LookupTable57, } from './tables.js';
/**
* Returns a template generator for the given template number
* @param template Template number
* @returns Template generator
*/
export function getGrib2Template5(template) {
switch (template) {
case 0:
return grib2Template50;
case 2:
return grib2Template52;
case 3:
return grib2Template53;
case 40:
return grib2Template540;
case 50:
return grib2Template550;
case 51:
return grib2Template551;
default:
throw new Error(`Template 5.${template} not defined`);
}
}
/**
* # Data Representation Template 5.0 - Grid point data - simple packing
*
* [Read more...](https://www.nco.ncep.noaa.gov/pmb/docs/grib2/grib2_doc/grib2_temp5-0.shtml)
* @param section
*
* ## Notes
* - Negative values of E or D shall be represented according to Regulation [92.1.5](https://codes.ecmwf.int/grib/format/grib2/regulations/).
* @returns - description of how to decode simple unpacked data
*/
export function grib2Template50(section) {
const originalType = section.getUint8(20);
let binaryScaleFactor = section.getUint16(15) & 0x7fff;
if (section.getUint16(15) >> 15 > 0)
binaryScaleFactor *= -1;
let decimalScaleFactor = section.getUint16(17) & 0x7fff;
if (section.getUint16(17) >> 15 > 0)
decimalScaleFactor *= -1;
return {
/** Reference value (R) (IEEE 32-bit floating-point value) */
referenceValue: section.getFloat32(11),
/** Binary scale factor (E) */
binaryScaleFactor,
/** Decimal scale factor (D) */
decimalScaleFactor,
/** Number of bits used for each packed value for simple packing, or for each group reference value for complex packing or spatial differencing */
numberOfBits: section.getUint8(19),
/** Type of original field values (see Code [Table 5.1](https://www.nco.ncep.noaa.gov/pmb/docs/grib2/grib2_doc/grib2_table5-1.shtml)) */
originalType: {
code: originalType,
description: grib2LookupTable51[originalType],
},
};
}
/**
* Data Representation Template 5.2 – Complex packing (no spatial differencing).
*
* Reads and parses the metadata fields defined by GRIB2 Template 5.2.
* For most templates, details of the packing process are described in Regulation 92.9.4.
* @see {@link https://www.nco.ncep.noaa.gov/pmb/docs/grib2/grib2_doc/grib2_temp5-2.shtml Template 5.2 documentation}
* @see {@link https://www.nco.ncep.noaa.gov/pmb/docs/grib2/grib2_doc/grib2_temp7-2.shtml Data template 7.2 for complementary info}
* @param section - Binary reader providing access to the section data.
* @returns Object containing the fields of Template 5.2.
*/
export function grib2Template52(section) {
/**
* Binary and decimal scale factors can be negative.
* They are stored with the sign bit in the high-order bit (bit 15).
*/
const originalTypeCode = section.getUint8(20);
let binaryScaleFactor = section.getUint16(15) & 0x7fff;
if (section.getUint16(15) >> 15 > 0)
binaryScaleFactor *= -1;
let decimalScaleFactor = section.getUint16(17) & 0x7fff;
if (section.getUint16(17) >> 15 > 0)
decimalScaleFactor *= -1;
// Fields unique to 5.2 (similar to 5.3, but no spatial differencing):
const groupSplittingMethodCode = section.getUint8(21); // Octet 22
const missingValueManagementCode = section.getUint8(22); // Octet 23
const primaryMissingValueSubstitute = section.getUint32(23); // Octets 24–27
const secondaryMissingValueSubstitute = section.getUint32(27); // Octets 28–31
const numberOfGroups = section.getUint32(31); // Octets 32–35
const referenceForGroupWidths = section.getUint8(35); // Octet 36
const groupWidthsBits = section.getUint8(36); // Octet 37
const referenceForGroupLengths = section.getUint32(37); // Octets 38–41
const groupLengthFactor = section.getUint8(41); // Octet 42
const trueLengthOfLastGroup = section.getUint32(42); // Octets 43–46
const nBitsGroupLength = section.getUint8(46); // Octet 47
return {
/** Reference value (R) (IEEE 32-bit floating-point). Octets 12–15 in the GRIB2 documentation. */
referenceValue: section.getFloat32(11),
/** Binary scale factor (E). Octets 16–17. */
binaryScaleFactor,
/** Decimal scale factor (D). Octets 18–19. */
decimalScaleFactor,
/**
* Number of bits per packed value for simple packing, or per group reference for
* complex packing. Octet 20 in the documentation.
*/
numberOfBits: section.getUint8(19),
/** Type of original field values. See Code Table 5.1. Octet 21. */
originalType: {
code: originalTypeCode,
description: grib2LookupTable51[originalTypeCode],
},
// Fields specific to complex packing (no spatial differencing):
/** Group splitting method used. See Code Table 5.4. Octet 22. */
groupSplittingMethod: {
code: groupSplittingMethodCode,
description: grib2LookupTable54[groupSplittingMethodCode],
},
/** Missing value management. See Code Table 5.5. Octet 23. */
missingValueManagement: {
code: missingValueManagementCode,
description: grib2LookupTable55[missingValueManagementCode],
},
/** Primary missing value substitute. Octets 24–27. */
primaryMissingValueSubstitute,
/** Secondary missing value substitute. Octets 28–31. */
secondaryMissingValueSubstitute,
/** Number of groups of data values (NG). Octets 32–35. */
numberOfGroups,
/**
* Reference for group widths. Octet 36.
* The group width is the number of bits used for every value in a group.
*/
referenceForGroupWidths,
/** Number of bits used for the group widths (after subtracting the reference value). Octet 37. */
groupWidthsBits,
/**
* Reference for group lengths. Octets 38–41.
* The group length (L) is the number of values in a group.
*/
referenceForGroupLengths,
/**
* Length increment for group lengths. Octet 42.
* Used in the formula: Lₙ = ref + Kₙ × len_inc.
*/
groupLengthFactor,
/**
* True length of the last group. Octets 43–46.
* A special-case group length if the sequence doesn’t fit the formula.
*/
trueLengthOfLastGroup,
/**
* Number of bits used for scaled group lengths (after subtracting ref
* and dividing by the length increment). Octet 47.
*/
nBitsGroupLength,
};
}
/**
* Data Representation Template 5.3 – Complex packing and spatial differencing.
*
* Reads and parses the metadata fields defined by GRIB2 Template 5.3.
* For most templates, details of the packing process are described in Regulation 92.9.4.
* See also:
* - [GRIB2 Template 5.3 documentation](https://www.nco.ncep.noaa.gov/pmb/docs/grib2/grib2_doc/grib2_temp5-3.shtml)
* - [Data template 7.3 and associated notes](https://www.nco.ncep.noaa.gov/pmb/docs/grib2/grib2_doc/grib2_temp7-3.shtml)
* - Spatial differencing (Regulation 92.9.4).
* @param section - Binary reader providing access to the section data
* @returns Object containing the fields of Template 5.3
*/
export function grib2Template53(section) {
/**
* Binary and decimal scale factors can be negative.
* They are stored with the sign bit in the high-order bit (bit 15).
*/
const originalTypeCode = section.getUint8(20);
let binaryScaleFactor = section.getUint16(15) & 0x7fff;
if (section.getUint16(15) >> 15 > 0)
binaryScaleFactor *= -1;
let decimalScaleFactor = section.getUint16(17) & 0x7fff;
if (section.getUint16(17) >> 15 > 0)
decimalScaleFactor *= -1;
// New fields introduced by Template 5.3
const groupSplittingMethodCode = section.getUint8(21);
const missingValueManagementCode = section.getUint8(22);
const primaryMissingValueSubstitute = section.getUint32(23);
const secondaryMissingValueSubstitute = section.getUint32(27);
const numberOfGroups = section.getUint32(31);
const referenceForGroupWidths = section.getUint8(35);
const groupWidthsBits = section.getUint8(36);
const referenceForGroupLengths = section.getUint32(37);
const groupLengthFactor = section.getUint8(41);
const trueLengthOfLastGroup = section.getUint32(42);
const nBitsGroupLength = section.getUint8(46);
const orderOfSpatialDifferenceCode = section.getUint8(47);
const extraDescriptorOctets = section.getUint8(48);
return {
/**
* Reference value (R) (IEEE 32-bit floating-point).
* Octets 12–15 in the GRIB2 documentation.
*/
referenceValue: section.getFloat32(11),
/** Binary scale factor (E). Octets 16–17. */
binaryScaleFactor,
/** Decimal scale factor (D). Octets 18–19. */
decimalScaleFactor,
/**
* Number of bits per packed value for simple packing,
* or per group reference for complex packing.
* Octet 20 in the documentation.
*/
numberOfBits: section.getUint8(19),
/** Type of original field values. See Code Table 5.1. Octet 21. */
originalType: {
code: originalTypeCode,
description: grib2LookupTable51[originalTypeCode],
},
// Fields specific to complex packing and spatial differencing:
/** Group splitting method used. See Code Table 5.4. Octet 22. */
groupSplittingMethod: {
code: groupSplittingMethodCode,
description: grib2LookupTable54[groupSplittingMethodCode],
},
/** Missing value management. See Code Table 5.5. Octet 23. */
missingValueManagement: {
code: missingValueManagementCode,
description: grib2LookupTable55[missingValueManagementCode],
},
/** Primary missing value substitute. Octets 24–27. */
primaryMissingValueSubstitute,
/** Secondary missing value substitute. Octets 28–31. */
secondaryMissingValueSubstitute,
/** Number of groups of data values (NG). Octets 32–35. */
numberOfGroups,
/**
* Reference for group widths. Octet 36.
* The group width is the number of bits used for every value in a group.
*/
referenceForGroupWidths,
/**
* Number of bits used for the group widths (after subtracting the reference value).
* Octet 37.
*/
groupWidthsBits,
/**
* Reference for group lengths. Octets 38–41.
* The group length (L) is the number of values in a group.
*/
referenceForGroupLengths,
/**
* Length increment for group lengths. Octet 42.
* Used in the formula: Lₙ = ref + Kₙ × len_inc.
*/
groupLengthFactor,
/**
* True length of the last group. Octets 43–46.
* A special-case group length if the sequence doesn’t fit the formula.
*/
trueLengthOfLastGroup,
/**
* Number of bits used for scaled group lengths (after subtracting ref
* and dividing by the length increment). Octet 47.
*/
nBitsGroupLength,
/** Order of spatial difference. See Code Table 5.6. Octet 48. */
orderOfSpatialDifference: {
code: orderOfSpatialDifferenceCode,
description: grib2LookupTable56[orderOfSpatialDifferenceCode],
},
/**
* Number of extra descriptor octets needed for spatial differencing
* (octets 6–ww in data template 7.3). Octet 49.
*/
extraDescriptorOctets,
};
}
/**
* Data Representation Template 5.40
*
* [Read more...](https://www.nco.ncep.noaa.gov/pmb/docs/grib2/grib2_doc/grib2_temp5-40.shtml)
* @param section - The raw section data to parse
* @returns - Parsed Data Representation Information
*/
export function grib2Template540(section) {
const originalTypeCode = section.getUint8(20);
const compressionType = section.getUint8(21);
return {
/** Reference value (R) (IEEE 32-bit floating-point value) */
referenceValue: section.getFloat32(11),
/** Binary scale factor (E) */
binaryScaleFactor: section.getInt16(15),
/** Decimal scale factor (D) */
decimalScaleFactor: section.getInt16(17),
/** Number of bits used for each packed value for simple packing, or for each group reference value for complex packing or spatial differencing */
numberOfBits: section.getUint8(19),
/** Type of original field values (see Code [Table 5.1](https://www.nco.ncep.noaa.gov/pmb/docs/grib2/grib2_doc/grib2_table5-1.shtml)) */
originalType: {
code: originalTypeCode,
description: grib2LookupTable51[originalTypeCode],
},
/** Type of Compression used. (see [Code Table 5.40](https://www.nco.ncep.noaa.gov/pmb/docs/grib2/grib2_doc/grib2_table5-40.shtml)) */
compressionType: {
code: compressionType,
description: grib2LookupTable540[compressionType],
},
/**
* Target compression ratio, M:1 (with respect to the bit-depth specified in octet 20),
* when octet 22 indicates Lossy Compression. Otherwise, set to missing.
*/
compressionRatio: section.getUint8(22),
};
}
/**
* # Data Representation Template 5.50 - Spectral data - simple packing
*
* [Read more...](https://www.nco.ncep.noaa.gov/pmb/docs/grib2/grib2_doc/grib2_temp5-50.shtml)
* @param section
*
* ## Notes
* - Removal of the real part of (0.0) coefficient from packed data is intended to reduce the
* variability of the coefficients, in order to improve packing accuracy.
* - For some spectral representations, the (0.0) coefficient represents the mean value of the
* parameter represented.
* - Negative values of E or D shall be represented according to Regulation [92.1.5](https://codes.ecmwf.int/grib/format/grib2/regulations/).
* @returns - description of how to decode simple unpacked data
*/
export function grib2Template550(section) {
let binaryScaleFactor = section.getUint16(15) & 0x7fff;
if (section.getUint16(15) >> 15 > 0)
binaryScaleFactor *= -1;
let decimalScaleFactor = section.getUint16(17) & 0x7fff;
if (section.getUint16(17) >> 15 > 0)
decimalScaleFactor *= -1;
return {
/** Reference value (R) (IEEE 32-bit floating-point value) */
referenceValue: section.getFloat32(11),
/** Binary scale factor (E) */
binaryScaleFactor,
/** Decimal scale factor (D) */
decimalScaleFactor,
/** Number of bits used for each packed value for simple packing, or for each group reference value for complex packing or spatial differencing */
numberOfBits: section.getUint8(19),
/** Type of original field values (see Code [Table 5.1](https://www.nco.ncep.noaa.gov/pmb/docs/grib2/grib2_doc/grib2_table5-1.shtml)) */
realPartCoefficientType: section.getFloat32(20),
};
}
/**
* # Data Representation Template 5.51 - Spectral data - complex packing
*
* [Read more...](https://www.nco.ncep.noaa.gov/pmb/docs/grib2/grib2_doc/grib2_temp5-51.shtml)
* @param section
*
* ## Notes
* - The unpacked subset is a set of values defined in the same way as the full set of values
* (on a spectrum limited to Js, Ks and Ms ), but on which scaling and packing are not applied.
* Associated values are stored in octets 6 onwards of section 7.
* - The remaining coefficients are multiplied by `(n x (n+1))p` , scaled and packed. The operator
* associated with this multiplication is derived from the Laplacian operator on the sphere.
* - The retrieval formula for a coefficient of wave number n is then: `Y = (R+X x 2e ) x 10-d x (n x(n+1))-p`
* where X is the packed scaled value associated with the coefficient.
* @returns - description of how to decode simple unpacked data
*/
export function grib2Template551(section) {
let binaryScaleFactor = section.getUint16(15) & 0x7fff;
if (section.getUint16(15) >> 15 > 0)
binaryScaleFactor *= -1;
let decimalScaleFactor = section.getUint16(17) & 0x7fff;
if (section.getUint16(17) >> 15 > 0)
decimalScaleFactor *= -1;
const precisionCode = section.getUint8(34);
return {
/** Reference value (R) (IEEE 32-bit floating-point value) */
referenceValue: section.getFloat32(11),
/** Binary scale factor (E) */
binaryScaleFactor,
/** Decimal scale factor (D) */
decimalScaleFactor,
/** Number of bits used for each packed value for simple packing, or for each group reference value for complex packing or spatial differencing */
numberOfBits: section.getUint8(19),
/** P ― Laplacian scaling factor (expressed in 10^-6 units) */
P: section.getFloat32(20),
/** Js ― pentagonal resolution parameter of the unpacked subset (see Note1) */
Js: section.getInt16(24),
/** Ks ― pentagonal resolution parameter of the unpacked subset (see Note1) */
Ks: section.getInt16(26),
/** Ms ― pentagonal resolution parameter of the unpacked subset (see Note1) */
Ms: section.getInt16(28),
/** Ts ― total number of values in the unpacked subset (see Note1) */
Ts: section.getInt32(30),
/** Precision of the unpacked subset (see Code Table 5.7) */
precision: {
code: precisionCode,
description: grib2LookupTable57[precisionCode],
},
};
}
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