# iMOD User Manual version 4.4 (html)

#### 9.9ISG-files

The ISG-file format is developed to capture all relevant information used by surface water elements in direct relation with groundwater. It stores stages, bottom heights, infiltration factors, resistances, and moreover, the actual outline of the surface water element. To store all these different types of information the ISG-file format consists of associated files that are connected by the ISG-file. This ISG-file is the one that will be actually read by iMOD, the other files will be opened by iMOD automatically. The syntax of the ISG-file format, and its associated files is as follows:

The structure of the ISG-file can be illustrated by the following figure:

Example of a single-precision ISG-file:

16,0,"Date","Water level","Bottom level","Resistance","Inf.factor"
"NOM_1",1,120,1,15,1,8,1,2,1,16
"NOM_2",121,18,16,7,9,3,3,2,17,8
"NOM_3",139,7,23,13,12,3,5,9,25,21
"NOM_4",146,6,36,4,15,1,14,2,46,5
"NOM_5",152,44,40,15,16,4,16,2,51,16
"NOM_6",196,16,55,8,20,3,18,2,67,9
"NOM_7",212,27,63,9,23,3,20,0,76,9
"NOM_8",239,31,72,12,26,4,20,4,85,16
"NOM_9",270,88,84,13,30,4,24,1,101,13
"NOM_10",358,10,97,6,34,1,25,1,114,6
"NOM_11",368,71,103,15,35,5,26,4,120,18
"NOM_12",439,11,118,32,40,10,30,0,138,31
"NOM_13",450,12,150,4,50,2,30,2,169,5
"NOM_14",462,30,154,6,52,2,32,1,174,6
"NOM_15",492,4,160,2,54,1,33,0,180,1
"NOM_16",496,15,162,5,55,2,33,1,181,5

Note: To maintain consistency do not edit a ISG-file outside iMOD.

For nodes, calculations points, cross-section, structures a similar setup is used. A first reference is made from the *.ISG file to the record in the *.ISD1 file. From there another reference is made to the *.ISD2 file that contains the specific configuration parameters.

The files associated from the ISG-file (ISP-, ISD-, ISC-, IST- and ISQ-files) are all binary and indexed files and cannot be edited in regular text editors. In the following sections these file-types will be described in detail.

##### 9.9.1ISP fileformat

The ISP-file supports single- and double precision syntax. In case single precision coordinates are used the ISP file is built with a record length of 8 bytes/2 words, for a double precision ISP file this is 16 bytes/4 words. The first record of the ISP is reserved to store the record length (2295 and 4343 for single- and double precision respectively). The ISEG variable in the ISG points to the record number that determines the first coordinate of the segment. Since the first record is reserved already, iMOD actually reads the ISEG+1 record instead. From each record two reals will be read that represent the x and y coordinate of the current node on the segment, see table below:

Attributes for each record in an ISP-file:

##### 9.9.2ISD1 and ISD2 fileformat

The ISD1-file supports single- and double precision syntax. In case single precision the ISD1-file is built with a record length of 44 bytes/11 words, for double precision this is 48 bytes/13 words. The first record is solely reserved to store the record length (11511 and 12535 for single- and double precision, respectively). The ICLC variable in the ISG-file points to the record number that determines the first calculation point on the segment. Since the first record is reserved already, iMOD actually reads the ICLC+1 record instead. Each record contains the following attributes:

Attributes for each record in an ISD1-file:

Note: For the SFR-option, only two calculation points are allowed, one at the beginning of a segment and one at the end.

It depends on the ASFR whether this file contains information for the RIV package (ASFR=0) or alternatively for the SFR package (ASFR=1). The ISD2-file is built with a record length of 20 bytes/5 words (single precision) and 36 bytes/9 words (double precision) for ASFR=0. For ASFR=1, the record length is 44 bytes/13 words (single precision) and 64 bytes/16 words (double precision). The first record is solely reserved to store the record length (ASFR=0: 5367/9463 and ASFR=1: 12535/16631). The IREF variable in the ISD1-file points to the record number that determines the data for the calculation point on the segment. Since the first record is reserved already, iMOD actually reads the IREF+1 record instead. Each record contains the following attributes:

Attributes for each record in an ISD2-file (ASFR=0):

Attributes for each record in an ISD2-file (ASFR=1):

##### 9.9.3ISC1 and ISC2 fileformat

The ISC1-file supports single- and double precision syntax. In case single precision the ISC1-file is built with a record length of 44 bytes/11 words, for double precision this is 48 bytes/12 words. The first record is solely reserved to store the record length (11511 and 12535 for single- and double precision, respectively). The ICRS variable in the ISG-file points to the record number that determines the first calculation point on the segment. Since the first record is reserved already, iMOD actually reads the ICRS+1 record instead. Each record contains the following attributes:

Attributes for each record in an ISC1-file:

The ISC2-file is built with a record length of 12 bytes/3 words for single precision and with 20 bytes/5 words for a double precision. The first record is solely reserved to store the record length (3319 and 5367 for single- and double precision, respectively). The IREF variable in the ISC1-file points to the record number that determines the data for the calculation point on the segment. Since the first record is reserved already, iMOD actually reads the IREF+1 record instead. Each record contains the following attributes whenever N$>$0:

Attributes for each record in an ISC2-file:

Alternatively, the record can have a different meaning whenever N$<$0:

##### 9.9.4IST1 and IST2 fileformat

The IST1-file supports single- and double precision syntax. In case single precision the IST1-file is built with a record length of 44 bytes/11 words, for double precision this is 48 bytes/12 words. The first record is solely reserved to store the record length (11511 and 12535 for single- and double precision, respectively). The ISTW variable in the ISG-file points to the record number that determines the first calculation point on the segment. Since the first record is reserved already, iMOD actually reads the ISTW+1 record instead. Each record contains the following attributes:

Attributes for each record in an IST1-file:

The ISC2-file is built with a record length of 12 bytes/3 words for single precision and with 20 bytes/5 words for a double precision. The first record is solely reserved to store the record length (3319 and 5367 for single- and double precision, respectively). The IREF variable in the IST1-file points to the record number that determines the data for the calculation point on the segment. Since the first record is reserved already, iMOD actually reads the IREF+1 record instead. Each record contains the following attributes:

Attributes for each record in an IST2-file:

##### 9.9.5ISQ1 and ISQ2 fileformat

The ISQ1-file supports single- and double precision syntax. In case single precision the ISQ1-file is built with a record length of 44 bytes/11 words, for double precision this is 48 bytes/12 words. The IQHR variable in the ISG-file points to the record number that determines the first calculation point on the segment. Since the first record is reserved already, iMOD actually reads the IQHR+1 record instead. Each record contains the following attributes:

Attributes for each record in an ISQ1-file:

The ISQ2-file is built with a record length of 12 bytes/3 words for single precision and with 20 bytes/5 words for a double precision. The first record is solely reserved to store the record length (3319 and 5367 for single- and double precision, respectively). The IREF variable in the ISQ1-file points to the record number that determines the data for the calculation point on the segment. Since the first record is reserved already, iMOD actually reads the IREF+1 record instead. Each record contains the following attributes:

Attributes for each record in an ISQ2-file: