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new 81c51ce8 Add note about NaN in matrix operations, calendar used by
java.time, enabling tests with EPSG database, and optional usage of GDAL.
81c51ce8 is described below
commit 81c51ce8e8f45bde3d9beb29dbe322881abd702c
Author: Martin Desruisseaux <[email protected]>
AuthorDate: Thu Jan 8 15:19:29 2026 +0100
Add note about NaN in matrix operations, calendar used by java.time,
enabling tests with EPSG database, and optional usage of GDAL.
---
content/code-patterns.md | 9 +++++++++
content/developer-guide/annexes/design/MatrixLibrary.html | 8 ++++++++
content/release-management.md | 2 +-
static/templates/release-announce.html | 5 +++--
4 files changed, 21 insertions(+), 3 deletions(-)
diff --git a/content/code-patterns.md b/content/code-patterns.md
index df61e025..dc43c534 100644
--- a/content/code-patterns.md
+++ b/content/code-patterns.md
@@ -50,6 +50,15 @@ Furthermore changes in pixel values may be lost if {@code
releaseWritableTile(
# International {#international}
+## Choose the right calendar {#calendar}
+
+Be aware that the parsing and formatting methods of `java.time.Instant` do not
use
+the same calendar as `java.text.DateFormat` for dates before October 15, 1582.
+The `java.time` classes use the proleptic Gregorian calendar while `java.text`
+switches to the proleptic Julian calendar before October 15, 1582.
+In particular, conversions between Julian days and dates require the Julian
calendar,
+i.e. the use of `java.text` instead of `java.time`.
+
## Specify timezone {#timezone}
Geospatial data often cover a wide geographic area, spanning many time zones.
diff --git a/content/developer-guide/annexes/design/MatrixLibrary.html
b/content/developer-guide/annexes/design/MatrixLibrary.html
index 852f4015..d273ffa2 100644
--- a/content/developer-guide/annexes/design/MatrixLibrary.html
+++ b/content/developer-guide/annexes/design/MatrixLibrary.html
@@ -61,6 +61,14 @@
The usual workaround is to compare floating point numbers with
some tolerance threshold.
Unfortunately it is difficult to choose a threshold that catch a
wide range of rounding errors
without wrongly considering legitimate datum shifts as rounding
errors (see previous point).</p></li>
+ <li><p>NaN (Not-A-Number) values need to be handled in a special way.
+ In standard IEEE 754 arithmetic, any operation involving a NaN
value produces NaN.
+ In Apache <abbr>SIS</abbr>, it is necessary to make a special case
where NaN × 0 = 0.
+ This arithmetic is correct when NaN is interpreted as a real and
finite value that should exist but is unknown
+ (note that this arithmetic would be incorrect if NaN could also
mean that the value does not exist at all or may be infinite,
+ but these interpretations are not used by Apache <abbr>SIS</abbr>
in the context of matrix operations for affine transformations).
+ The NaN × 0 operation happens when an axis does not depend on the
coordinate having a NaN value,
+ in which case it is important to have NaN × 0 = 0.</p></li>
</ul>
<p>
As a consequence of above points, accuracy of a matrix library is more
important than performance for a <abbr>GIS</abbr> like Apache <abbr>SIS</abbr>.
diff --git a/content/release-management.md b/content/release-management.md
index 17639097..eac8ec32 100644
--- a/content/release-management.md
+++ b/content/release-management.md
@@ -327,7 +327,7 @@ Then, execute the following commands and fix as much
warnings as practical:
```bash
systemctl start postgresql.service # Optional — exact command depends
on Linux distribution.
-export SIS_TEST_OPTIONS=extensive,postgresql
+export SIS_TEST_OPTIONS=epsg,extensive,postgresql
gradle test
```
diff --git a/static/templates/release-announce.html
b/static/templates/release-announce.html
index 9a823ff9..39c8b35e 100644
--- a/static/templates/release-announce.html
+++ b/static/templates/release-announce.html
@@ -15,9 +15,9 @@
availability of the <abbr title="Spatial Information System">SIS</abbr>
$VERSION release.
</p><p>
The release can be obtained from the Apache <abbr title="Spatial
Information System">SIS</abbr>
- download page - https://sis.apache.org/downloads.html
+ download page — https://sis.apache.org/downloads.html
</p><p>
- Release notes are available at -
https://sis.apache.org/release-notes/$VERSION.html
+ Release notes are available at —
https://sis.apache.org/release-notes/$VERSION.html
</p><p>
Apache <abbr title="Spatial Information System">SIS</abbr> is a Java
language library for developing geospatial applications.
<abbr title="Spatial Information System">SIS</abbr> provides data
structures for geographic features and associated metadata
@@ -32,6 +32,7 @@
<li>Read netCDF-3, Cloud Optimized GeoTIFF (including BigTIFF) and
Moving Feature CSV data formats</li>
<li>Read/write GPX, ASCII Grid, World File, ISO 19115-3 metadata and
legacy ISO 19139 compliant XML documents</li>
<li>Leverage Cloud Optimized formats (GeoTIFF) for smaller downloads
from HTTP and Amazon S3 storage service</li>
+ <li>Optionally use the GDAL library for two-dimensional raster formats
not supported by Apache SIS.</li>
<li>Referencing by coordinates (ISO 19111) or by identifiers (ISO
19112)<ul>
<li>Well Known Text (WKT) version 1 and 2 (ISO 19162)</li>
<li>Geographic Markup Language (GML) version 3.2 (ISO 19136)</li>
