The three Survival maps are Hospital, Swamp, Settlement. The difficulty level increases from Hospital to Swamp to Settlement as you must defend 1, 2, and 3 bases, respectively.

Enemies in on the Hosipital are the late game of the non-dlc levels (Pacific campaign) meaning Martian weapons are far superior to these enemies. Enemies of both Swamp and Settlement are the same strength in Martain campaign. Enemies gain health each round with Big Willie having thousands of hit points in rounds 80+.

Version 1.0
Everything is text with some formatting. I may add pictures at some point if enough people are interested.
This guide tends to be information heavy. I tried to add in capital letters to things to help draw your eyes to important parts.
I may add in more specific goals/strategies for each map if I have the time.
If I can gain access to the source, I will add in the waves for each round. Until then I won't do it by hand.

Early rounds on all 3 maps are simple to finish using an Assault build. I suggest the Karlsson Mk V for its 3 left and 3 right slots. I would also suggest 2 Snipers for range (Super Indirect Sniper Cannon is a decent pick with Ricochet+ until you get Albert. Ricochet+ bounces your shots multiple times and can hit enemies multiple times -once per bounce). The 2 open slots on each side can be whatever ever machine gun or shotgun that helps the most. For legs, the Fortify+/Quickload are the best. Use whatever turrets(emplacements) you feel comfortable with until you get the feel what works.

Once you finish the basic prep gear, pick up the Honeychurch Mk IV or the Selker Mk V if you sold it or miraculously didn't find either yet. Switch your legs to the Speedy Biped legs as Sprint+ gives you a big mobility boost.

Depending on what Engineering Trench you plan on using will determine the other emplacements/weapons you need to pick up.

Selker
• Massive Mine Layer
  
• Super Shredder Turret
  
• Green Emplacement of choice (Camo Shotgun is nice :P)

Honeychurch
• Dampening Generator Mk III
  
• Impeccable Collection Pod
  
• Green Emplacement of choice (Machine guns for Knobs/Cathys are nice)

If you have read the Basic Prep section, you should understand that Engineering Chassis are the only way to get to high level rounds. Assualt chassis won't carry you far past 30 (if you're lucky) and Meduims won't do much better (if any).

Place your turrets above Knob level. Always try to place your turrets on elevated surfaces so that Knobs (and Amps) cannot reach them. If you fill up space and have no where to throw your Sniper Turrets use Machine Gun Turrets to distract the Knobs and protect your Snipers. Avoid throwing them close to pathways where Burst Transmitters may shoot them too. If you can't keep them out of the Burst Transmitter range, at least keep them out of Knob range and keep an eye on your Turrets if you need to protect them.

Always target Jacobs. Watch for their name and listen for a high pitched whine from their shield. Jacobs tend to be the last target on the priority list for the Turret AI. Generally the AI will only attack Jacobs when no other mobs are in its sight line. Mine Layers and Piercing Sniper Turrets increase the chance Jacobs will take damage but you will personally have to deal with them quite often. Jacobs tend to pace themselves with the slowest unit by them but due to pathing issues they may ignore units that are close behind them and sprint ahead to catch up to another unit instead.

Each round contains the same enemy count but they can spawn from different gates - For example the second wave of Settlement is a Blitzer wave(if I got the number right) - I would still like to verify this through the source but I don't have access. On Hospital and Swamp, it doesn't tend to change your placements much and make you run around. On Settlement, it will force you to run back and forth because you cannot predict the spawns and your turrets cannot cover everything. Some spawns are consistent on what gate they spawn on though. You may have to retry few times to get the hang of an optimal turret placement.

Amps tend to be free sources of scrap as they often get stuck trying to path to turrets out of their range. Pathfinding in this game isn't very fancy in the first place but the Amp AI acts like someone took a hammer to it. Experiment to see what gets them stuck because it makes rounds much easier when one boss becomes imbolized.

Wave trends, once you get the general feel of the level and start progressing, you will notice wave trends which vary slightly per map. These trends are most noticeable because they spawn the same bosses the same way each time. Usually these waves either punish because you missed the Jacobs or reward you with tons of scrap from killing all the boss mobs. One particular trend wave is a count of 3 Big Willie each accompanied by its own 3-4 Jacobs. These Willies will spawn within a few seconds of each other which can cause disaster if you across the map and can't kill the Jacobs fast enough or if your Turret damage is lacking

Useful emplacements. Other emplacements either have a low utility, their DPS is too low, or they are too inconsistent despite maybe having better range or total damage.

• Massive Mine Layer - Massive damage with AoE helps kill Jacobs and knock tons of health off boss mobs. As an Engineer, it costs 72 scrap to place but only 48 to upgrade. Gains additional 2 mines per upgrade which not only increases its total damage but the rate it deploys the mines as well (Need to run a frame count but it is straightforward watching the animation). Cannot be targeted/destroyed by mobs (Camo).
  
  
• Piercing Sniper - Primary damage dealing turret. Piercing allows it to dish out damage to more mobs at the cost of a few damage per shot compared to the Ironclad Sniper.
  
  
• Dampening Generator III - Slows down mobs with good range. Gives you and your turrets some breathing space
  
  
• Super Shredder Turret - Helps defend Knobs and cheap sacrificial turret if needed. Chance to generate extra scrap can be useful but is rarely noticed.
  
  
• Impeccable Collection Prong - Saves you from missing out on scrap and scrambling around the map. Cannot be targeted/destoryed by mobs (Camo). Only downside is your turrets may get in the way if someone is using Mine Layers (Not an issue solo though)
  
  
• Camo Shotgun - Sacrifices damage compared to Ironclad Shotgun so that it cannot be targeted by Turret killing mobs. Cheap 40 scrap cost with ok damage and range makes it a nice starter placement on earlier rounds or where Snipers/Machine guns aren't viable. (Only useful to Selker)
  
  
• Laser Turret - Only useful if you have a friend with you. Normally outclassed in power by the Piercing Sniper Turret. This turret shines most when you have multiple attacking a swarm of enemies. The damage tick rate is very high (more ticks = More damage per second) and hits more enemies consistently than the Piercing Sniper because of the continious beam. Lack of range doesn't make it practical on Settlement.

Useful Weapons. These weapons beat the competition due to their utility and overall dps. Other weapons may seem viable, but these are tried and true. Other shotguns/machineguns either lack range or fail to compete in damage output.

• Muerte Fiesta Numero 6 - Highest DPS weapon in game without extra modifiers (Pierce/Ricochet/etc.). True range of 200 (not 75) gives a good reach. High fire rate with 6 shots and good damage make it shine. Does require you to move around more often though.
  
• Albert - Only viable on the Honeychurch. Good damage and range with pierce+ makes it incredibly useful at hitting Jacobs. Only drawback is its fire rate so don't miss.

Only applies to multiplayer.
In multiplayer you share scrap. For 2 people, every 2 scrap that either player picks up nets each of you one scrap. While you can vary the emplacements you bring, it makes communication for turret placements key. If your partner wastes or holds their scrap, you are playing with half of the normal scrap. (For 3 players, its 3 scrap for 1, 4 players, 4 for 1)

As a general rule, as long as communication is good, more players is easier since you can occupy different parts of the map and not lack coverage in case a wave starts to make it past your defenses and you need to pitch in.

These are two primary strategies to beat round 99. Things will vary between levels but general play is the same.

Honeychurch Strat 1
Honeychurch outfitted with

• Albert / 2x Muerte
  
• Speedy Biped Legs
  
• Super Shreder Turret (vary if needed)
  
• Piercing Sniper Turret
  
• Impeccable CollectionProg
  
• Dampening Generator III

This strategy attempts to lose any scrap and slow enemies in order to give you time to build/upgrade and assist your snipers.

Remember to keep your Dampening Generators and Sniper Turrets out of harms way as frequently as possible. Start off by placing a sniper turret in the location with the best coverage or killing Tubes yourself. Manually collect the scrap. Once you have a couple to a few sniper turrets down, focus on placing Collection Prongs. These have camo and cannot be destroyed so just place them in a killing field where they won't block other turret placements or get scrap stuck against walls. Build/upgrade more Snipers and then start placing Dampening Generators. This will help you give you time to run around the map and kill the Jacobs as well as buy your snipers time to pick off heavier enemies. (Or at least that's the idea, I personally didn't play this way but some of my friends did)

Selker Strat 2
Selker outfitted with

• 2x Muerte
  
• Speedy Biped Legs
  
• Super Shreder Turret*
  
• Piercing Sniper Turret
  
• Massive Mine Layer
  
• Camo Shotgun*
  *note - can be varied but I find these useful

This strategy requires a lot of watching and moving since you still need to kill Jacobs and now collect your own scrap ( Nani !!), however the build cost for the same/more dps from your placements compared to the Honeychurch strategy is much less costly.

Again remember to keep your Sniper Turrets out of harms way. Start off by placing a Sniper in a spot with good coverage and move to clean up enemies and collect scrap. After you get a few snipers, start placing Massive Mine Layers along travel paths. I find it best to start where enemies tend to make it the furthest as it reduces your need to move as far to collect scrap. Focus on placing a consistent stream of mines while occassionally upgrading or placing a Sniper. Don't over focus mines on one pathway since you will run out of scrap and leave your base vurneable. Once you have a few Mine Layers per path. Upgrade them. For a negligible upgrade cost, their damage will sky rocket. Keep up with your other turrets as necessary then start placing mine layers on the spawn gates as best as you can. Again, avoid over focusing on one gate. The mine layers on top of the gates will make you move towards gates to pick up scrap but they will kill Jacobs that spawn before a wave and potentially hit Jacobs spawning in the middle, meaning you can kill the Jacobs much faster. Keep expanding the mine field and your snipers. (This is my primary style and I have successfully done Wave 99 on Hospital and Swamp. I almost finished wave 97 on Settlement until a Volt Dropper ignored me twice and shot my lowest health base two different times)