From 9d79f79757c6e976e7ad2f9818b81e8f706cab8b Mon Sep 17 00:00:00 2001
From: WendelHime <wendelhime@hotmail.com>
Date: Fri, 6 Nov 2020 15:07:08 -0300
Subject: [PATCH] move tags to bottom part of IFD and add description with
 source

---
 v2/tags_data.go | 28 +++++++++++++++++++---------
 v3/tags_data.go | 28 +++++++++++++++++++---------
 2 files changed, 38 insertions(+), 18 deletions(-)

diff --git a/v2/tags_data.go b/v2/tags_data.go
index 3a58d4c..bcc9d92 100644
--- a/v2/tags_data.go
+++ b/v2/tags_data.go
@@ -564,18 +564,9 @@ IFD:
   name: FNumber
 # NOTE(dustin): SRATIONAL isn't mentioned in the standard, but we have seen it in real data.
   type_names: [RATIONAL, SRATIONAL]
-- id: 0x830e
-  name: ModelPixelScaleTag
-  type_name: RATIONAL
 - id: 0x83bb
   name: IPTCNAA
   type_name: LONG
-- id: 0x8482
-  name: ModelTiepointTag
-  type_name: RATIONAL
-- id: 0x85d8
-  name: ModelTransformationTag
-  type_name: RATIONAL
 - id: 0x8649
   name: ImageResources
   type_name: BYTE
@@ -918,6 +909,25 @@ IFD:
 - id: 0xc74e
   name: OpcodeList3
   type_name: UNDEFINED
+# This tag may be used to specify the size of raster pixel spacing in the model space units, when the raster space can be embedded in the model space coordinate system without rotation, and consists of the following 3 values:
+#    ModelPixelScaleTag = (ScaleX, ScaleY, ScaleZ)
+# where ScaleX and ScaleY give the horizontal and vertical spacing of raster pixels. The ScaleZ is primarily used to map the pixel value of a digital elevation model into the correct Z-scale, and so for most other purposes this value should be zero (since most model spaces are 2-D, with Z=0).
+# Source: http://geotiff.maptools.org/spec/geotiff2.6.html#2.6.1
+- id: 0x830e
+  name: ModelPixelScaleTag
+  type_name: RATIONAL
+# This tag stores raster->model tiepoint pairs in the order
+#	ModelTiepointTag = (...,I,J,K, X,Y,Z...),
+# where (I,J,K) is the point at location (I,J) in raster space with pixel-value K, and (X,Y,Z) is a vector in model space. In most cases the model space is only two-dimensional, in which case both K and Z should be set to zero; this third dimension is provided in anticipation of future support for 3D digital elevation models and vertical coordinate systems.
+# Source: http://geotiff.maptools.org/spec/geotiff2.6.html#2.6.1
+- id: 0x8482
+  name: ModelTiepointTag
+  type_name: RATIONAL
+# This tag may be used to specify the transformation matrix between the raster space (and its dependent pixel-value space) and the (possibly 3D) model space.
+# Source: http://geotiff.maptools.org/spec/geotiff2.6.html#2.6.1
+- id: 0x85d8
+  name: ModelTransformationTag
+  type_name: RATIONAL
 IFD/Exif/Iop:
 - id: 0x0001
   name: InteroperabilityIndex
diff --git a/v3/tags_data.go b/v3/tags_data.go
index 3a58d4c..bcc9d92 100644
--- a/v3/tags_data.go
+++ b/v3/tags_data.go
@@ -564,18 +564,9 @@ IFD:
   name: FNumber
 # NOTE(dustin): SRATIONAL isn't mentioned in the standard, but we have seen it in real data.
   type_names: [RATIONAL, SRATIONAL]
-- id: 0x830e
-  name: ModelPixelScaleTag
-  type_name: RATIONAL
 - id: 0x83bb
   name: IPTCNAA
   type_name: LONG
-- id: 0x8482
-  name: ModelTiepointTag
-  type_name: RATIONAL
-- id: 0x85d8
-  name: ModelTransformationTag
-  type_name: RATIONAL
 - id: 0x8649
   name: ImageResources
   type_name: BYTE
@@ -918,6 +909,25 @@ IFD:
 - id: 0xc74e
   name: OpcodeList3
   type_name: UNDEFINED
+# This tag may be used to specify the size of raster pixel spacing in the model space units, when the raster space can be embedded in the model space coordinate system without rotation, and consists of the following 3 values:
+#    ModelPixelScaleTag = (ScaleX, ScaleY, ScaleZ)
+# where ScaleX and ScaleY give the horizontal and vertical spacing of raster pixels. The ScaleZ is primarily used to map the pixel value of a digital elevation model into the correct Z-scale, and so for most other purposes this value should be zero (since most model spaces are 2-D, with Z=0).
+# Source: http://geotiff.maptools.org/spec/geotiff2.6.html#2.6.1
+- id: 0x830e
+  name: ModelPixelScaleTag
+  type_name: RATIONAL
+# This tag stores raster->model tiepoint pairs in the order
+#	ModelTiepointTag = (...,I,J,K, X,Y,Z...),
+# where (I,J,K) is the point at location (I,J) in raster space with pixel-value K, and (X,Y,Z) is a vector in model space. In most cases the model space is only two-dimensional, in which case both K and Z should be set to zero; this third dimension is provided in anticipation of future support for 3D digital elevation models and vertical coordinate systems.
+# Source: http://geotiff.maptools.org/spec/geotiff2.6.html#2.6.1
+- id: 0x8482
+  name: ModelTiepointTag
+  type_name: RATIONAL
+# This tag may be used to specify the transformation matrix between the raster space (and its dependent pixel-value space) and the (possibly 3D) model space.
+# Source: http://geotiff.maptools.org/spec/geotiff2.6.html#2.6.1
+- id: 0x85d8
+  name: ModelTransformationTag
+  type_name: RATIONAL
 IFD/Exif/Iop:
 - id: 0x0001
   name: InteroperabilityIndex