Satellite, and soon UAV, images of areas devastated by hurricane Matthew are becoming available. To map visible damage, it is proposed to use BAR methodology, adapted for OSM.
This project is for an area around Jérémie, where damage to the city have already been mapped by Copernicus and Pacific Disaster Center (PDC). Pleiades imagery acquired within the framework of the International Charter Space and Major Disasters is available for OSM mapping.
In summary, this methodology takes into account structure categories visible in the imagery, sorted in:
- Light strength structures (the most vulnerable);
- Medium strength structures (moderately vulnerable) and;
- Heavy strength structures (usually the least vulnerable).
Each structure is also assigned a damage scale, which is as follows:
- No visible damage to the structure;
- Minimal visible damage: Visible partial roof damage;
- Significant visible damage: The roof has suffered significant damage or is completely off, but the walls remain standing;
- Critical visible damage: The walls and the roofs are down and the structure integrity is completely compromised.
Aerial photos are also available, particularly over Jérémie city, and make it possible to calibrate classification from satellite imagery to more detailed views where they are available. Available maps from Copernicus and PDC can also been used as training reference.
Created by jgc - Updated - Priority: low
- Entities to Map
- bâtiments (dégâts subis) / Buildings (damage)
- Changeset Comment
- #llgtm-tache-44 When saving your work, please leave the default comment but add what you actually mapped, for example "added buildings and a residential road".
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If you are not yet familiar with the BAR methodology, please first take the time to read:
It contains a description of concepts, and a complete set of examples, for each structure category and damage scale, that is not repeated here, but with which you should be familiar before proceeding. The illustrated exemples from Vanuatu are not too different from Haiti - except for the criteria for light and medium structures (see below), and help to classify and evaluate buildings.
You can use aerial views of Jérémie on this uMap for alternative points of view.
"BAR Damage Assessment" preset and style are available in the presets and styles lists integrated in JOSM. Activate them in Edit / Preferences / Map Settings / Map Paint Styles and Tagging Presets. They make it easier to apply the appropriate tags, and to visualize them.
When how to classify a structure, or how to scale damage, is not clear to you, or for any question you may have, please come and discuss it on available discussion channels most convenient to you: Skype help chat (please ask to be included sending an email to jgc at arkemie dot org), IRC #hot channel on oftc.net, Mumble on arkemie.org, Twitter direct messages with @jgVisov, etc.
You are advised to split your tile if it contains any group of buildings, to be able to give full attention to the buildings it contains. A smaller initial size was not selected for the tiles only because it would have produced many small useless tiles in empty areas.
Map all the buildings, using Bing as common geometrical reference (or other imagery that was used for OSM mapping of these area): In addition to usual tags (e.g. at least “building=...”), use the following tags - that can be set easily using the above preset - to record information for the BAR method, and follow-up data management life cycle:
damage=[none|minimal|significant|complete|unidentified] (“visible” is implicitly understood)
damage:assessment=[initial-date|revision-date] (e.g. “2016-10-07”)
source:damage=Pleiades 2016-10-07, CNES, Airbus DS
(combined with any other source of information, such as geo-localizable photos, separated with a “;”)
If you feel that you cannot assign a structure category or a damage scale, use the value 'unidentified'. Please come and discuss these cases, in the discussion channels given above.
Regarding the post-Matthew Pleiades images layer, if you add “_nir” after the date in the URL for Pleiades image, you can get another layer, with near infrared (NIR) as red, which is useful to see vegetation.
Here are relevant extracts from the BAR methodology study:
Assigning structure categories:
"Light Structures: This category, annotated with a triangle, encompasses structures that are built predominantly from light material or locally sourced materials. These structures may be mobile or possess no real hard roof, in some cases, roofs are made of metal or light material; they are often small in size. As such, these structures are likely to be the most vulnerable structures in any impacted region. Examples of these types of structures can include huts, tukuls or mobile trailers.
Medium Structures: This category, annotated with a circle, encompasses structures that are built from semi-hard materials or mixed products. These structures have solid frames built using wood, steel or cement. These type of structures are fixed and possess hardened walls and roofs which can be made out of wood or cement. Unlike light structures, these types of structures are able to withstand moderate level of wind, with no to little damage, while maintaining their structural integrity. These types of structures can be individual or multi family houses, small stores, places of worship and similar structures.
Heavy Structures: This category, annotated with a square, encompasses structures that are built from hard materials such as reinforced cement and steel. Infrastructure of this type is the least structurally vulnerable in any observed region. These structures are designed to withstand high level winds without receiving heavy damage or endangering the structural integrity of the structure. In many areas, these may include multiple story buildings, strip malls, hospital buildings, or public utilities."
Proposed criteria for cyclone Winston impact on Fiji:
(Adapted from the criteria of the case study for cyclone Pam impact on Vanuatu. In Fiji, it appears that the vast majority of structures have metal roofs.)
The light structures category is assigned to structures of relatively small size, and low build complexity, built using, cinder blocks, bricks, organic or locally sourced material.
The medium structures category is assigned to medium sized structures, with higher build complexity (with additions built on, fortifications, etc.), single- or multi-level, built using cement walls.
The heavy structures category is assigned to larger structures, with higher build complexity and/or multi-level, built using cement walls or prefabricated material.
Assigning Damage Scale
"The Signal Program BAR Methodology applies a color-coded damage scale across all structure types based on repeating, visible damage patterns. Damage in the BAR scale is classified in 4 distinct categories: Green, Yellow, Orange and Red.
No Visible Damage: This category, classified by the color green, signifies no visible damage to the structures. In these cases, the roof is virtually undamaged and the walls, in effect, remain standing. The structure appears to have complete structural integrity and does not appear to need repair.
Minimal Visible Damage: This category, classified by the color yellow, signifies that some minimal visible damage has been sustained. In these structures, the roof remains largely intact, but presents partial damage to the roof’s surface, with minimal exposure beneath. In oblique aerial and satellite imagery, minimal damage may be able to be observed within the structure and to the exterior walls. The structure appears to have general structural integrity but needs minor repairs.
Significant Visible Damage: This category, classified by the color orange, signifies that partial but extensive visible damage has been sustained. In these structures, the roof is entirely damaged or missing. The walls of the structure remain upright. However, the interior wall partitions can be partially damaged. Debris inside the structure can also potentially be visible. The structure does not appear to have complete structural integrity and is in need of significant repair.
Critical Visible Damage ['complete'] : This category, classified by the color red, signifies severe visible damage has been sustained. In these structures, the roof is completely destroyed or missing, and the walls have been destroyed or collapsed. The support structures are completely leveled, and interior objects have also suffered visibly heavy damage or destruction. The structure does not appear to have any structural integrity and requires comprehensive reconstruction or demolition of the entire structure.
In the Case study for cyclone Pam impact on Vanuatu:
"The “No Visible Damage” category was applied to structure that appear virtually undamaged with no identifiable damage to the roof or the walls.
The “Minimal Damage” category was applied to the structures that appear to have sustained limited damage with only parts of the roof appearing to be either damaged or missing.
The “Significant Damage” category was applied to structures that appear to have sustained damage with large parts of the roof damaged or missing. These structures, however, remain standing with the walls appearing largely intact
The “Critical Damage” ['complete'] category was applied to structures that have completely lost their roofs and have sustained heavy damage to their walls. These structures have sustained massive damage to their structural integrity and have largely or completely collapsed."